Crumble chorizo into a small skillet; cook and stir over medium heat until fully cooked. Drain. Stir in 1/3 cup cheese and cilantro.
Rub cut side of garlic clove over bread slices; discard garlic. Place bread in a greased 13-in. x 9-in. baking dish. Top with tomatoes, meat mixture and remaining cheese.
In a large bowl, whisk the eggs, milk, salt, pepper, onion powder and pepper flakes. Pour over casserole.
Bake, uncovered, at 350° for 35-45 minutes or until a knife inserted near the center comes out clean (cover loosely with foil if top browns too quickly). Let stand for 10 minutes before cutting. Yield: 12 servings.