Baked in a cake pan, this tortilla is easier and better tasting than skillet cooked ones.
5 T extra virgin olive oil
5-6 medium Yukon Gold potatoes, peeled, quartered, and cut crosswise into 1/8-inch-thick slices
1 small onion , halved and sliced thin
1 t salt
Fresh ground black pepper
10 large eggs
1 red pepper, roasted, rinsed and diced (or 1/2 cup jarred roasted red peppers , rinsed, dried, and diced)
OPTIONAL: cooked greens like chard, diced chorizo, bacon or prosciutto, asparagus tips or fresh green peas
Line a 9-inch cake pan with a piece of parchment paper. Preheat oven to 350.
Toss potatoes, onion, ½ teaspoon salt, and pepper with 3 T of the olive oil in large bowl until potato slices are thoroughly coated. Heat 2 T oil in 10-inch nonstick skillet over medium-high heat until shimmering. Reduce heat to medium-low, add potato mixture to skillet, and set bowl aside without washing. Cover and cook, stirring with rubber spatula every 5 minutes, until the potatoes are tender, about 20 minutes.
Now prep your add-ins. I like it just with roasted red pepper (fresh or, in a pinch, jarred ones). But know this: you must first sauté or thoroughly drain and dry it before adding it to the eggs.
Whisk eggs and remaining ½ teaspoon salt in reserved bowl. Using rubber spatula, fold hot potato mixture, red peppers, and any other add-ins you like into eggs. Pour into the parchment-lined 9-inch cake pan and bake for 30-40 minutes until puffed up and golden. Allow to cool for about 5 minutes, then invert onto a large, flat plate. Remove the parchment paper, invert onto a second plate (or foil-wrapped cake circle) for service. Serve at room temperature.