Thinly slice potatoes into ¼-inch rounds for even cooking, then seed and cut red and green peppers into ½-inch strips. Pat dry to avoid splatter.

Warm olive oil in a nonstick skillet over medium heat. Add potatoes, season with salt, and cook about 10 minutes until edges turn golden brown and tender.

Stir in peppers (plus diced onion or garlic if using). Sauté 5 minutes until peppers soften and show a slight char around the edges.

In a bowl, whisk large eggs with a pinch of salt and pepper until pale and frothy, about 1 minute.

Gently pour whisked eggs over the potato-pepper mix, tilting the pan for even coverage. Reduce heat to medium-low and cook until edges start to set, about 3 minutes.

Cover the pan with a large plate, invert tortilla onto it, then slide back into the skillet uncooked side down. Cook another 2–3 minutes until firm and golden.

Slide the tortilla onto a cutting board. Let rest 2 minutes, slice into wedges, garnish with parsley or extra peppers, and serve warm or at room temperature.