A tortilla is simply a Spanish version of a fritatta: enjoy it for breakfast, lunch, or dinner.  My Oven-Baked Mediterranean Tortilla combines Spanish and Greek flavors - lots of caramelized Vidalia onions, chives, basil, baby arugula and diced yams.  It's all held together by eggs, yogurt and a crumble of Feta cheese. Yum. The tortilla keeps