- 1 cup extra-virgin olive oil
- 3 medium russet potatoes (about 1 3/4 pounds total), peeled and cut into 1/8-inch-thick slices
- 1 medium onion, halved lengthwise and cut into 1/8-inch-thick slices
- Coarse salt and freshly ground pepper
- 7 large eggs
Heat oil in a 10-inch nonstick slope-sided skillet or omelet pan over medium heat. Toss together potatoes, onion, and 1 teaspoon salt in a medium bowl. Add to warm oil; cover, and cook, stirring occasionally, until potatoes are tender, about 12 minutes (do not let the onion brown). Pour into a sieve set over a medium bowl; set oil aside.
Lightly beat eggs in a medium bowl with 1 teaspoon salt and 1/4 teaspoon pepper. Add potato mixture, and let stand, stirring occasionally, 10 minutes.
Heat 2 teaspoons reserved oil in clean skillet over medium heat. Add egg-and-potato mixture; cook, pulling cooked egg away from sides with a rubber spatula to let raw egg flow underneath, until bottom is set and just pale golden (and top is almost set), 5 to 7 minutes. Place a plate, upside down, over skillet (use a plate with a diameter larger than the skillet); invert tortilla onto the plate.
Add 1 teaspoon reserved oil to skillet; swirl to coat. Slide tortilla, uncooked side down, back into skillet. If any potatoes slip out from bottom, tuck them back in. Cook, pressing down on tortilla with spatula and tucking in edges to shape sides, until completely cooked through, 4 to 6 minutes more. Slide onto a cutting board. Let cool slightly. Serve warm or at room temperature, cut into wedges.