One of Spain’s bitterest battles, a long-festering confrontation that predates the ugly international skirmishes over paella and even the rivalry between Real Madrid and FC Barcelona, could finally be reaching its endgame.

The town council of Betanzos, the Galician municipality whose tortillas de patatas, or Spanish omelettes, are regularly hailed as the finest in the land, has spoken. And the message to those entering this year’s tortilla competition is simple: leave out the onions.

The issue of whether cebollas belong in the emblematic fried dish runs like a faultline under the nation’s bar stools and dining tables, dividing families and communities and pitting concebollistas (with-onionists) against sincebollistas (without-onionists).

Authorities in the town claim they are only staying true to their roots with the competition rules. “We want to be faithful to the Betanzos tradition of potatoes, oil, egg and salt,” they told La Voz de Galicia. “Nothing more.”

However, local bars taking part in tortilla week but not entering the annual contest are free to deploy onions. “That’s fine on the route but not in the competition,” the council said. “We brought it up with the bar owners and the vast majority of them were behind the idea.”

Alberto García, a local chef who has twice won the prize for Betanzos’s best tortilla, knows his onions – and when to leave them out. His recipe also triumphed in national tortilla competitions in 2011 and 2017, a sincebollista David against the concebollista Goliath.

“When it comes to onion, the cookbooks say a Spanish omelette’s ingredients are egg, potato, olive oil, salt and onion,” he told the Guardian. “But to be honest, Betanzos has become famous for its omelettes because of a local woman, Señora Angelita, who cooked them without onion more than a century ago.”

For García, who runs the Mesón O’Pote restaurant in the town, it is all something of a baseless controversy. “I think the council’s just trying to make Betanzos stand out by not including onion,” he said. “What makes our omelette different and delicious is having properly fried potatoes and really juicy, runny eggs.”

Unusually for a chef in a country that will ruthlessly defend its culinary traditions against Jamie Oliver and even the odd foreign ambassador, García is happy to mix things up. Sit down in his restaurant and ask for a bit of onion or chorizo in your tortilla and he will oblige. But the chef insists certain cooking methods must be respected.

“If it doesn’t have onion, it doesn’t have onion. If it has onion, it has onion. Look, I’m not saying onion is good or bad. But there is a correct way of cooking, cutting and serving tortilla: the egg has to be really, really runny and the potato has to be perfectly golden – properly fried. It doesn’t really matter if it it’s got a bit of onion or chorizo in.”

García hasn’t taken part in the local competition for a few years now, since upgrading his bar to a proper restaurant. He thinks it’s time to look beyond the tortilla as a tapa and agree that a “majestic tortilla” should also be considered a proper table dish and afforded the same reverence and respect as a suckling pig from Segovia or a pot of Galicia’s eponymous broth.

“Ask me if there’s anything more important in Betanzos right now than tortillas and I’ll tell you, hand on heart, that there isn’t,” he said. “It’s our economic motor, so we need consensus. What truffles are to Piedmont, tortilla is for Betanzos.”

A brief wander through its streets would confirm as much, García said. “People in this town will talk in bars and shops about who’s the better player – Ronaldo or Messi? But they’ll also argue over which place does the best tortilla. We live off tortilla here.”

Alberto García’s tortilla de patatas recipe (serves four):

12 Galician free-range eggs

800g chopped potatoes, preferably Kennebec. If out of season, any variety that fries well

Extra virgin olive oil

Salt

Fry the potatoes well in the oil at 160-180C until golden, then mix with the gently beaten eggs and leave to sit for around three minutes. Bring the frying pan up to temperature, then, at the last minute, add salt to the unctuous egg and potato mixture. Add the mixture to the pan and turn it right down.

After a quick, 30-second fry, turn the tortilla once (use a plate). Cook for another minute or so, turn again, then wait 10-15 seconds before turning for the third and final time. Turn off the pan and let the tortilla cook in the residual heat for 15-20 seconds. Your tortilla is done.