Cheesy Ground Beef & Cauliflower Casserole

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

Heat oil in a large oven-safe skillet over medium heat. Add onion and bell pepper; cook, stirring, until softened, about 5 minutes. Add beef and cauliflower; cook, stirring and breaking the beef up into smaller pieces, until it is no longer pink, 5 to 7 minutes. Stir in garlic, chili powder, cumin, oregano, salt and chipotle; cook until fragrant, about 1 minute. Add 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 cheese over the beef mixture and top with sliced jalapeños. Broil until the cheese is melted and browned in spots, 2 to 3 minutes.