8 large eggs
2 cups olive oil
1 1/2 lb yukon gold potatoes, peeled, halved and thinly sliced crosswise
3/4 lb yellow onions, thinly sliced
Beat eggs with a pinch of salt until frothed. Set aside.
Begin preheating a 10 inch nonstick pan on medium high heat. Once shimmering, add the potatoes and onions and should gently bubble. Regulate the pan to allow this gentle bubbling and stir occasionally until potatoes and onions are extremely tender, about 25 minutes. Set a mesh strainer over a bowl and drain the potatoes and onions of excess oil.
Transfer potatoes and onions to a bowl and season with salt, stirring well. Re beat eggs until frothy again and add the potato mixture. Stir very well and set aside for 5 minutes.
Clean the skillet used for the potato and onions and add 3 tbsp of reserved oil to the skillet and heat on medium high heat. Once shimmering, add the egg mixture to the pan and cook while swirling and shaking the pan rapidly, until the bottom and sides begin to set, about 3 minutes. Press the edges towards the middle and continue to cook until beginning to set again around the edges, about 3 minutes more.
Place a large plate on top of the pan and set your hand on top and invert the tortilla onto it. Add 1 additional tbsp of reserved oil and return to heat. Slide the tortilla back in the pan and cook until starting to firm up, about 2 minutes more. If desired, this process can be repeated 2-3 times more to cook more evenly.
Slide the tortilla out onto a clean plate or invert like before and let stand for 5 minutes before serving. Cut into wedges and serve.