This traditional Mexican dish was originally devised as a way to use stale corn tortillas. Serve with margaritas in glasses rimmed with chipotle salt.
1. Preheat oven to 400°F. Place white onion, tomatoes, and garlic in single layer on baking sheet. Roast 25 minutes, or until onions begin to brown and tomato skins wrinkle. Meanwhile, toss tortilla strips with oil and spread on separate baking sheet. Bake 15 minutes. Sprinkle with salt. Cool tortillas and vegetables 20 minutes.
2. Peel tomatoes and place in food processor with white onions and garlic. Add chipotles and 1 Tbs. adobo sauce; purée until smooth, and season with salt and pepper.
3. Spread thin layer of tomato mixture in bottom of 1½-qt. baking dish. Add tortillas in single layer. Top with black beans, corn, red onion, and cheese. Cover with remaining sauce, and bake 25 to 30 minutes, or until bubbly.
4. Whisk together sour cream and lime juice, and drizzle over chilaquiles.