Tortilla Española

In a large saucepan, cover the potatoes with cold water, add 1 teaspoon of salt and bring to a boil over high heat. Reduce the heat to moderate and simmer until the potatoes are just tender, about 7 minutes. Drain the potatoes and rinse under cold running water to stop the cooking; drain again. Spread the potato slices on paper towels and pat dry.

Preheat the oven to 400°. In a heavy 12-inch ovenproof skillet, heat 2 tablespoons of the oil. Add the onions and cook over moderate heat, stirring often, until golden brown, 10 to 15 minutes.

In a large bowl, lightly beat the eggs. Gently stir in the potatoes and onions and season generously with salt and pepper.

Heat the remaining 2 tablespoons of oil in the skillet. Add the egg mixture and cook over moderate heat undisturbed until the bottom of the tortilla is lightly browned, about 2 minutes. Transfer the skillet to the oven and bake the tortilla for about 20 minutes, or until the eggs are set and the potatoes are very tender. Remove from the oven and let cool for 5 minutes.

Loosen the tortilla from the pan by running the tip of a knife around the edge. Place a round platter over the pan and invert. Cut into wedges and serve.