Tortilla de Patatas

Heat the oil in a 9-inch skillet; add potatoes, one slice at a time so that they don't stick. Alternate layers of potato and onion. COOK slowly, medium flame. DO NOT FRY! Turn occasionally until potatoes are tender, but NOT brown. They must be loose, not "in a cake".

Beat eggs in a large bowl with a fork until slightly foamy. Salt to taste.

Drain the potatoes in a colander reserving 3 tbsp of the oil. Add potatoes to beaten eggs, pressing them so that eggs cover them completely. Let mixture sit for 15 minutes.

Heat 2 tbsps of the reserved oil in large skillet. Add potato-egg mixture, spreading quickly. Lower the heat to medium-high. Shake pan to prevent sticking (crucial step!) When potatoes start to brown, put a plate on skillet and turn around, adding another tbsp. of oil.

Brown on the other side. Can flip three or four times for better cooking.