Tortilla (the spanish omelette, not the mexican bread) can be absolutely gorgeous, and it doesn't require much in the way of ingredients so it's really handy. Because of the potatoes it's really chunky, much more of a meal than your average omelette. The amounts given here serve 3 or 4 and fit nicely into a 12" frying pan when you're making it.
3 or 4 potatoes, washed (but not peeled)
1 red onion
4 tbsp olive oil
A handful of frozen peas
Warm up the olive oil in a frying pan. Slice the potatoes into chunks about 1cm thick and then parboil them - that is, drop them into a pan of boiling water and cook them only for about 5 minutes. While this is happening, chop the onion into thick chunks too, and break the eggs into a bowl and mix them up a bit.
Drain the potatoes in a colander or sieve, and leave them to drain while you gently fry the onion in the frying pan. When the onions have softened (3 or 4 mins?) add the drained potatoes and stir around. Leave these to fry for 3 or 4 more minutes before turning them over. Sprinkle the peas into the pan and get everything evenly spread out. Add some salt and pepper if you like. Turn on the grill to a hot setting.
Pour the eggs into the pan, trying to pour the mixture as evenly as possible. Do not stir at all from this point on! The pan should be on a medium heat as the eggs start to cook at the bottom. Let them cook for about 5 minutes. It's tricky to judge when to stop because you can't check underneath to see if they look done, but you can tell it's OK when the egg mixture starts to look a little bit cakey and set.
Take the pan off the heat and put it under the grill to cook the top (3 or 4 mins). Then turn it out onto a plate. Slice it up to serve, and have it with bread and butter and salad leaves.