Most Spanish home cooks enjoy their tortillas warmed through but still runny, custardy, and jiggly in the center, then set and lightly browned on the exterior. (You might notice tortillas displayed under or behind glass cases in tapas bars are sometimes cooked more because of salmonella fears, says Lalo Beltran, a chef at Barcelona Cooking.) To test yours for doneness before you remove it to a plate, press a finger against the center of the tortilla to measure the amount of give—you want it to be soft and tender but not fully soupy. Remember, the eggs will continue to cook slightly after you remove the pan from the heat. Slide it out onto a plate, always presenting tortilla with the first side you seared facing up.