In Houston, ask for a tortilla, and you're likely to be answered with "Flour or corn?" -- not eggs. But the tortilla espagnola ($3 per slice) at Barcino Seafood and Tapas(8899 Katy Freeway, 713-490-8899) is a kind of traditional Spanish omelet, and one of that country's most popular dishes. A large deep frying pan is lined with alternating layers of cooked potatoes and caramelized onions, with eggs binding everything together and making a crust on the bottom. The result is a sort of layered cake -- or torta, which explains the dish's name. Served with a mildly spiced red-pepper sauce, the tapa-size version served here is perfect for a light lunch.