Tortilla

Peel and thinly slice an onion and two large potatoes, dry them, then put in a hot pan with olive oil. Toss, lower the heat, cover and cook until tender (app. 20 mns). Avoid letting them brown. 

Then transfer to a bowl in which you've previously whisked together 5 eggs and some seasoning.

Return it all to the pan (in which you've added more oil), and cook uncovered on low heat for 20-25 minutes. Turn over the tortilla (with a plate or flat lid), cook another 2-3 mns, remove from heat and let settle before serving.