In a large mixing bowl, beat the eggs with a whisk or a fork and add 1/2 tsp salt. Set it aside.

Peel and slice the onions.

Peel and cut the potatoes. We used a food processor to slice them but you can do it by hand with a knife if you don’t have a food processor or use the slicing part of the box grater.

In a pan, over medium-high heat, add 4 tbsp (1/4 cup) of olive oil. When the oil is shimmering, turn the heat down to medium and add the sliced onions and potatoes and cover with the lid. Traditionally, you would submerge them in olive oil and fry them in olive oil. But that means you’d need 2-4 cups of oil. In Spain, people reuse this oil for 5-6 other fryings or uses. We’ll try to make them without the use of so much oil.

Cook the potatoes and onions for 10 minutes over medium heat, stirring every 60 seconds and making sure the onions and potatoes don’t burn. We like a bit of color/caramelization but you can decide how much color/caramelization you like on them.

Add 1/2 tsp kosher salt and 1/2 tsp ground black pepper and turn the heat to medium-low and cook the mixture until the potatoes and onions are fully cooked (about 10 minutes). Stir every minute or two to make sure the potatoes and onions don't burn.

Take a bit of the potatoes and onions and add them to the egg mixture, stirring. Repeat a bit at a time until you've added all the potatoes and onions to the eggs.

Let the egg-potato-onion mixture rest for 2-3 minutes and then add it back to the pan over low heat and put a lid on.

Cook the bottom for about 5-6 minutes. Losen up the sides, pulling so the egg goes on the bottom and cooks better.

Put a large plate on the pan and flip the omelette onto the plate.

Slide the omelet back into the pan and cook on medium heat for about 2 minutes until the bottom is cooked. Plate it up and cut it into slices, tapas-style!