As distinct from the Mexican tortilla, the Spanish tortilla (or Spanish omelette) is a thick fried potato pancake, eaten hot or cold. Watch this recipe being made in the Allrecipes Classic Spanish Tortilla Video.
Great basic recipe for tortilla, very similar to ones I've had in Spain! - 06 Aug 2012 (Review from Allrecipes UK & Ireland)
Yum! - 12 Feb 2015 (Review from Allrecipes UK & Ireland)