Preparation

• In a cast-iron skillet or Dutch oven, heat the olive oil over low heat. Meanwhile, peel and slice the potatoes about 1∕8-inch thick and place into a bowl.

• Increase the heat to medium and add the potato slices. Meanwhile, thinly slice the onion and add to the potatoes. Continue to cook until the potatoes are soft and the onion is translucent, about 15 minutes. Remove from heat.

• With a slotted spoon, transfer the potatoes and onion to a large bowl. Season with salt and pepper to taste and let cool. Strain the oil into a container and reserve.

• In a large bowl, whisk the eggs. Add the eggs to the cooled potato mixture and stir gently to combine.

• To a 12-inch cast-iron skillet over high heat, add the reserved olive oil until the skillet is filled to ¼-inch. When the oil is hot, add the potato-egg mixture. Using a heat-proof rubber spatula, smooth out the mixture and scrape around the edges of the pan to help shape the tortilla.

• Reduce the heat to medium-low and continue to cook, occasionally shaking the pan and running the spatula around the edges to shape the tortilla and prevent sticking, until the edges are set, 15 to 20 minutes.

• Cover the skillet with a flat lid or a large plate and flip the tortilla out of the skillet. Slide the tortilla back into the skillet and cook the other side, continuing to shape with the spatula, until golden brown, 10 to 15 minutes. Remove from heat and let cool to room temperature.

• Meanwhile, make the sweety drop pepper aioli by stirring together the mayonnaise, sweety drop peppers, lemon juice, Dijon mustard, garlic and salt to taste in a small bowl.

• Flip the tortilla onto a platter and cut pie-shaped pieces. Bring the platter, or wrap individual slices in deli paper for serving at a picnic. Serve with a dollop of the aioli and trout roe, if desired.