Peel and slice potatoes and onions very thinly and mix in bowl with a liberal pinch of salt. (I use a mandoline to slice, because it’s quick and uniform.) Heat olive oil in a 10” nonstick skillet or cast-iron skillet over medium heat. When the oil is hot, drop in one potato slice, and if it starts to sizzle around the edges, add remaining potatoes and onions, and reduce heat to low. Add more olive oil, if necessary, until potato and onions are covered. Turn often and adjust heat as necessary to prevent burning. Potatoes are done when they can be easily pierced. (Note that freshly harvested potatoes will likely cook faster than store-bought ones.)

While this is cooking, beat eggs in a large bowl, big enough to add potatoes and onions to later. Add a pinch of salt to eggs.

When the potatoes are ready, gently drain in a colander, trying not to break them too much. (If drained over a bowl, you can reserve the flavor-rich oil for use in other dishes.) Allow potatoes to cool for a few minutes while excess oil drains, then add potatoes to beaten eggs, gently folding them in. Let this sit for 10 minutes while the potatoes absorb the eggs.

Heat a skillet over medium flame and add 1-2 tablespoons of the reserved oil. Add potato mixture to skillet, reduce heat to medium-low, and cook for 7-10 minutes, making sure you can loosen edges with a spatula.

At this point, you can decide if you want to invert the tortilla onto a plate and slide it back into skillet or if you prefer to put pan in 375℉ oven. To invert skillet, wear oven mitts and cover skillet with large plate or skillet lid. Invert skillet swiftly and carefully slide tortilla back into skillet to continue cooking for a few minutes, then invert again onto serving plate. If you opt for cooking in oven, cook for 3-5 minutes until eggs are set, not overcooked, and serve directly from skillet.

This dish is best served at room temperature with a dollop of sour cream or aioli on the side.