In a rare moment of national unity unseen since a certain British chef recklessly floated the idea of adding chorizo to paella, Spain has come together at last to settle one of its most ancient, vexed and divisive questions. No longer will tempers flare at bar counters nor arguments rive friends, families and neighbours gathered together at table. Chefs, critics and home-cooks can put aside their opinions – and their spatulas – safe in the knowledge that yes, an overwhelming majority of Spaniards really do prefer their tortilla de patatas with onion. On Wednesday, El Mundo published the results of a survey into the humble but deeply revered Spanish omelette that delighted the country’s concebollistas (with-onionists) and left a disagreeable aftertaste in the mouths of its sincebollistas (without-onionists). The poll was unequivocal: 72.7% of those surveyed favoured onion; 25.3% were against, and a non-committal 1.9% didn’t answer. The issue also cut across party lines in a country whose politics are increasingly fragmented, bitter and polarised. Of those who support the Spanish Socialist Workers’ party, 73.2% are pro-onion, as are 72.1% of those who vote for the conservative People’s party, 69.4% of voters for the far-right Vox party, 65% of those who vote for the far-left, anti-austerity Unidas Podemos party, and 74.1% of those who vote for Citizens, a centre-right party whose recent electoral performances suggest it may very soon have had its chips. Women are slightly more likely to favour onion than men (73.3% to 72.2%), while support for the allium addition rises from 65.8% among those aged 18 and 26 to a peak of 75% among those between 45 and 64. In a sign that he was only too aware of the explosive nature of the material he was publishing, Gonzalo Suárez, the editor of El Mundo’s daily magazine section, tweeted the cover with the plea: “All I ask is that you accept victory in a sporting manner and defeat in a stoical one.” Some on social media couldn’t hide their disappointment – “Tortilla de patatas with onion isn’t tortilla de patatas – it’s a tortilla with stuff”; some crowed – “Kneel, sincebollistas!”, and some urged the paper to weigh in on whether pineapple belonged on pizza. There was also the occasional voice of sense: “We need to learn how to listen to and understand the sincebollistas. Brexit and Trump happened because of less.” In 2018, the town council of Betanzos – the Galician municipality whose tortillas de patatas are often seen as the finest in the country – stipulated that those entering that year’s high-profile competition should use only potatoes, oil, egg and salt. Those who know their onions, however, were not surprised by the poll. For Teresa Cuerda, who was gearing up for lunch at Casa Dani, the famous Madrid tortilla bar her sister and brother-in-law opened in 1991, the survey was merely the official confirmation of an old and familiar truth. “Tortilla with onion has always been far more popular at Casa Dani than tortilla without onion,” said Cuerda. “I’d say around 90% of our customers prefer their tortilla with onion.” The restaurant – whose staff make 300 to 400 tortillas each weekday, and as many as 700 a day at the weekend – knows what its customers like. “I think tortilla with onion tastes better because it makes it a bit juicier,” said Cuerda. “But you don’t really notice the onion in our tortilla and it doesn’t dominate. It’s a very gentle flavour because of the kind of onion we use. There are actually a lot of people who don’t like onion but who do like our tortilla with onion.” The secret of a good tortilla, she added, was using high-quality ingredients and thinking about the kind of omelette you want to make. Some Spaniards favour a firm, set omelette, while others prefer an oozy, eggy mess with the consistency of a recently breached dam. “Not all potatoes are the same and neither are all onions or eggs. Some eggs, for example, have too much water. We’ve spent 30 years choosing the best ingredients for the tortillas we make.” Both the onions and the potatoes need to be well fried, said Cuerda, and well mixed. But even then, even the finest ingredients will only get you so far. “You need a good frying pan and a good hand,” she said. “But of course, a good cook will also play their part.”