Prep: 1. Peel and slice potatoes and onion. Make: 1. Heat oil over medium-high heat in a non-stick pan. Add potatoes and onions and cook, lifting and turning, until potatoes are soft but not brown, about 20 minutes. 2. Meanwhile beat eggs. 3. Remove potatoes and onions from pan with a slotted spoon and add to eggs. 4. Pour off all but 1 tablespoon of the oil (reserve oil) and re-heat over medium heat. Add egg and potato mixture, spreading potatoes evenly in the pan. Cook uncovered until the bottom is lightly browned, about 3 minutes. 5. Gently slide a spatula along edges and underneath the torta. Slide the torta onto a large plate. Add 1 teaspoon of reserved oil to pan (not so much that it drips, and flip the torta back into the pan (uncooked side down). Continue cooking over medium heat until eggs are just set, about 3 minutes. 6. Cut into wedges and serve at room temperature.
Don't be intimidating by the flipping, it takes a little care but isn't actually that hard. If you prefer you can also just reduce the heat a little and cover it. You won't get the same crispy edges that distinguish a torta from a frittata but it will still be delicious.