The Spanish omelette is the same dish as the tortilla española, Spain’s iconic thick omelette of eggs, potatoes, and olive oil. Sliced potatoes, and often onion, are slowly poached in abundant olive oil until tender, then mixed with beaten eggs and cooked into a deep, golden disc, flipped to cook both sides. Served in wedges at room temperature, it is the star of tapas bars, picnics, and family tables across Spain. The great debate is onion or no onion, a question that divides households. Whether served just set and juicy or cooked through, it is humble food elevated by technique: eggs, potatoes, oil, salt, and patience.