Cheesy Ground Beef & Cauliflower Casserole

Position rack in upper third of oven. Preheat broiler to high.

Heat 1 tablespoon oil in a large broiler-safe skillet over medium heat. Add ½ cup onion and 1 bell pepper; cook, stirring, until softened, about 5 minutes. Add 1 pound beef and 3 cups cauliflower; cook, stirring and breaking the beef up into smaller pieces, until it is no longer pink, 5 to 7 minutes. Stir in 3 cloves garlic, 2 tablespoons chili powder, 2 teaspoons cumin, 1 teaspoon oregano, ½ teaspoon salt and ¼ teaspoon chipotle; cook until fragrant, about 1 minute. Add 15 ounces diced tomatoes and their juices; bring to a simmer and cook, stirring occasionally, until liquid is reduced and the cauliflower is tender, about 3 minutes more. Remove from heat.

Sprinkle 2 cups cheese over the beef mixture and top with ⅓ cup sliced jalapeños. Broil until the cheese is melted and browned in spots, 2 to 3 minutes.