A hearty Spanish omelet filled with potatoes, peppers, and onions is a protein-rich, vegetarian-friendly breakfast or dinner. This family-friendly dish is filling, flavorful, and rooted in Mediterranean tradition.
Peel and thinly slice the potatoes and onion; thinly slice the red bell pepper as well for even cooking.
Heat 3 tbsp olive oil in a 10-inch nonstick skillet over medium heat. Add potatoes, onions, and bell pepper with 1/2 tsp salt. Stir to coat; cover and cook on medium-low, gently turning every 3 minutes until potatoes are just tender but not browning, about 12 minutes.
In a large bowl, whisk the eggs with 1/2 tsp salt and black pepper until well mixed. Gently fold the warm drained potato-pepper mixture into the eggs. Let sit for 2 minutes to allow flavors to meld.
Wipe the skillet and add remaining 1 tbsp olive oil; heat over medium-high until shimmering. Pour in the egg and vegetable mixture and agitate the pan gently for 30 seconds with a rubber spatula to prevent sticking.
Reduce heat to medium-low and cook undisturbed for 5–6 minutes, running spatula around edges to loosen. When almost set, invert the omelet onto a plate, then slide it back into the skillet. Cook another 2–3 minutes to finish and ensure the center is just set.
Slide the omelet onto a cutting board, cool 2 minutes, garnish with parsley, then slice into wedges and serve warm or at room temperature.