8medium potatoes,peeled and cut into ¾ pieces inch (I used russet potatoes)
2small onions,halved and thinly sliced
McCormick freshly ground black pepper,to taste
Heat the oil in a medium (9 inch) nonstick skillet over medium-low heat. Cook potatoes, turning occasionally, until soft, about 10-15 minutes. Add onion and mix to incorporate. Add 1 teaspoon of salt and black pepper to taste; cook until onion is translucent and fragrant, and the potatoes are lightly golden, about 5 minutes. Remove carefully the potatoes and onion, with a slotted spoon, from the skillet and place on a large plate. Remove the oil from the skillet, leaving only 2 to 3 tablespoons of oil to cook the tortilla.
In a large bowl add the eggs white and whisk vigorously until the mixture is frothy and increased in size, about 3 minutes. Stir in egg yolks, and the remaining teaspoon of salt; mix until incorporated. Add potatoes with onion and mix.
Slightly heat the oil in the skillet over low heat. Add the eggs and potatoes mixture. Cover and cook for 10-15 minutes, or until the tortilla is almost set. Check that the tortilla is cooked on the bottom and not sticking to the skillet. Invert tortilla using a large plate, then slide it back into the skillet and cook the other side for 5 -8 minutes, or until fully cooked.
Cut the tortilla and serve warm or at room temperature.