Spain’s most famous food argument, whether the tortilla de patatas should be made con cebolla o sin cebolla, with onion or without, is usually presented as an eternal national quarrel split down the middle. It is neither eternal nor evenly split. Two serious national surveys put the onion side ahead by roughly 70 points to 25, and the documentary record undercuts both camps at once: the first written Spanish tortilla recipe, printed in 1599, contained onion but no potato, while the earliest documents describing an actual potato tortilla, from 1767 and 1817, mention no onion at all.
That matters because “tradition” is the weapon both sides reach for first. The sincebollistas, the purists who want no onion, insist the original recipe was potato and egg alone. The concebollistas, the onion partisans, answer that the tortilla has always been made with whatever sweetens it. Both arguments collapse the moment you open the actual sources. If you repeat either version at a Spanish bar, you are repeating a myth, and in a country where this question has been put to professional pollsters more than once, the myths are checkable.
This article works from the primary record: Diego Granado’s 1599 cookbook, digitized by the Biblioteca Nacional and catalogued in the Real Academia Española’s digital archive, the 1767 agronomy treatise of José Antonio Valcárcel, the 1817 petition to the Cortes de Navarra first surfaced by José María Iribarren in the journal Príncipe de Viana in 1956, and the two modern polls that measured the debate directly: Sigma Dos for El Mundo in 2021 and Spain’s state pollster, the CIS, in 2023.
The Score Is Not Close: What the Polls Actually Say
For a debate this loud, remarkably few people cite the numbers. In July 2021, the polling firm Sigma Dos measured the question for El Mundo and found that 72.7 percent of Spaniards prefer their tortilla de patatas con cebolla, against 25.3 percent who want it without. The preference held across sex, age bracket, and even declared party vote. The closest the sincebollistas came to parity was among the youngest respondents, aged 18 to 26, where the onion still won 65.8 percent.
Two years later the Centro de Investigaciones Sociológicas, the Spanish state’s own survey institute, put the same question into its first ever tourism and gastronomy survey, study 3419, published in September 2023. The result was practically identical: 70.4 percent with onion. Two independent methodologies, two years apart, landing within about two points of each other is as settled as public opinion gets.
The same CIS study measured the debate the onion question usually eclipses, the cooking point. Only 53.9 percent of Spaniards want their tortilla poco hecha, soft and barely set in the middle, while 26.9 percent want it fully cooked through. In other words, Spain agrees on the onion far more than it agrees on the texture, which is the opposite of what the noise level of each argument would suggest.
1599: The First Written Tortilla Recipe Had Onion and No Potato
The oldest known written recipe for a tortilla in Spain appears in the Libro del arte de cozina by Diego Granado Maldonado, first printed in 1599 and today digitized in the Biblioteca Nacional and indexed by the Real Academia Española. Granado, a cook born in Valencia in 1574 who served the Habsburg court, describes a tortilla de huevos con tocino: onions cooked in the embers, chopped fine and fried in pork lard with diced bacon, then bound with eggs beaten with soft cheese, pepper, cinnamon, and herbs, and finished, in full Golden Age style, with orange juice poured over the top.
Note what is in that recipe and what is not. The onion is there from the first page of the tortilla’s written history. The potato is nowhere, for the simple reason that in 1599 the potato was still a botanical curiosity in Spain, an American import that Europeans would not trust as food for nearly two more centuries. Anyone claiming the “original tortilla” as ammunition should sit with the fact that the original tortilla was onion, lard, bacon, cheese, cinnamon, and orange juice.
The tortilla española as the world now knows it, potato and egg in olive oil, had to wait for hunger to do its work. Only when famine pressed on late eighteenth century Spain did the potato move from garden oddity to staple, and only then did it fall into the frying pan.
1767 and 1817: When the Potato Finally Arrived, the Onion Went Silent
The earliest authentic documented mention of a potato tortilla in Spain dates to 1767, in the third volume of Agricultura general y gobierno de la casa de campo by the agronomist José Antonio Valcárcel. Writing about a potato variety from La Mancha, he notes that in Spain its usual use was “in stews, and tortillas.” That single line, surfaced in recent years by the food historian Ana Vega, also quietly demolishes the best known origin claim: Villanueva de la Serena in Badajoz proclaims itself the birthplace of the tortilla de patatas on the strength of a 1798 proposal by Joseph de Tena Godoy, but that document describes something closer to a fried potato bread, and Valcárcel’s tortillas predate it by three decades.
The most vivid early document belongs to Navarra. A petition deposited for the Cortes de Navarra on 14 May 1817, one of the anonymous complaint papers known as memoriales de ratonera, describes what rural Navarrese farm families actually ate: two or three eggs in a tortilla for five or six people, stretched with potatoes, scraps of bread, “or other things.” It is the first known description of the potato tortilla as the everyday food of ordinary people, and Navarra holds it. The full story of that document, and of how the tortilla operates during the fiesta, is told in our companion piece on the first written record of the tortilla española.
Here is the detail both camps skip: neither the 1767 mention nor the 1817 memorial says a word about onion. The poor families stretching three eggs across six mouths added whatever they had, which is precisely why claiming a single canonical recipe for this dish is ahistorical. The tortilla was born improvised.
Betanzos: The Strongest Argument the Sin Cebolla Camp Has
If the polls make the concebollistas look unbeatable, the sincebollistas hold one card the numbers cannot touch: the tortilla most often crowned the best in Spain contains no onion at all. In Betanzos, a small town in A Coruña, Galicia, the local style is strict: potatoes and eggs only, the eggs barely beaten, the whole thing pulled off the heat while the center is still almost liquid. Bars like O Pote have made the town a pilgrimage destination, and Betanzos runs an annual competition where jugosidad, juiciness, and fidelity to the recipe decide the winner.
The professional kitchen leans the same way more often than the public does. Dabiz Muñoz, whose Madrid restaurant DiverXO holds three Michelin stars, put the purist position bluntly in 2024: the Spanish tortilla does not carry onion, and the version with onion “is something else.” Plenty of celebrated chefs take the opposite view, and Spanish food media regularly line the two camps up against each other, but the pattern is real: the debate’s elite wing skews sin cebolla while the country at large votes con.
That tension is the honest summary of the whole argument. The onion wins the vote and loses the trophy. Anyone who tells you the question is settled in one direction is only reading half the scoreboard.
What You Will Actually Get in Pamplona
Order a pintxo de tortilla at a bar counter in Pamplona’s Casco Viejo and you will usually not be asked for a position on the great debate. Most bars make one house tortilla, and whether it carries onion depends on the kitchen, not on you. The practical move is to ask “¿lleva cebolla?”, does it have onion, and take the answer with the good humor the question deserves. During San Fermín the tortilla works as fuel more than philosophy: it appears at the bar counter from early morning alongside the carajillo that Pamplona treats as breakfast, and a wedge of it is one of the most reliable things you can eat between events.
The tortilla pintxo also makes a useful measuring stick for a bar. A place that respects its tortilla, whichever camp it belongs to, tends to respect the rest of its counter, a rule of thumb worth carrying through the pintxo bars of Pamplona during any visit.
FAQ
Does authentic Spanish tortilla have onion?
There is no single authentic recipe, and the historical record cuts against both purist positions. The first written Spanish tortilla recipe, from 1599, contained onion but no potato, because the potato was not yet eaten in Spain. The earliest documents describing a potato tortilla, from 1767 and 1817, do not mention onion. The dish began as improvised poverty food, stretched with whatever a family had, so “authentic” can honestly describe both versions.
What percentage of Spaniards prefer tortilla with onion?
About seven in ten. A Sigma Dos poll for El Mundo in 2021 found 72.7 percent prefer tortilla de patatas with onion versus 25.3 percent without, and Spain’s state pollster, the CIS, found 70.4 percent with onion in its 2023 tourism and gastronomy survey. The preference holds across age, sex, and political affiliation, with the youngest adults the least enthusiastic about onion but still favoring it.
What is a concebollista and a sincebollista?
They are the humorous partisan labels Spaniards use for the two camps in the tortilla debate. A concebollista defends the tortilla made with onion, and a sincebollista defends the version without. The words are recent coinages born on the internet, built from con or sin plus cebolla plus the ending ista, and they are documented in Spanish lexicographic references such as Wikcionario.
Is tortilla de Betanzos made with onion?
No. The Betanzos style, from the town of Betanzos in A Coruña, Galicia, is strictly potatoes and eggs, with no onion, cooked so briefly that the interior stays almost liquid. It is regularly named the best tortilla in Spain, which gives the sin cebolla camp its strongest single argument despite losing the national polls by a wide margin.
Every article on the Encierro blog is authored or reviewed by active bull runners with direct experience in Pamplona.