How to Make It
Heat oven to 450° F. On a rimmed baking sheet, toss the bell peppers and garlic with 1 tablespoon of the oil and ¼ teaspoon each salt and black pepper. Roast until tender, 12 to 14 minutes.
Meanwhile, heat the remaining tablespoon of oil in a large skillet over medium-high heat. Add the onion and ½ teaspoon salt and cook, stirring occasionally, until beginning to brown, 3 to 5 minutes. Add the beef, corn, and chili powder and cook, stirring occasionally, until the beef is browned, 6 to 8 minutes more.
Divide the beef mixture among the tortillas and top with the avocado, Cheddar, salsa, and cilantro. Serve with the bell peppers and lime wedges.