Step 1

Preheat oven to 375 degrees. Spray a 9" X 13" baking pan with nonstick spray.

Step 2

Pulse cauliflower in a blender until reduced to rice-sized pieces, working in batches as needed.

Step 3

Bring an extra-large skillet sprayed with nonstick spray to medium heat. Cook and stir cauliflower until partially softened, 6 - 8 minutes.

Step 4

Transfer cauliflower to a large bowl. Add 1/2 cup cheese, 1 tsp. cumin, 1/2 tsp. chili powder, 1/2 tsp. salt, and 1/8 tsp. each onion powder, garlic powder, and paprika. Mix thoroughly.

Step 5

Evenly transfer cauliflower mixture to the baking pan, and smooth out the surface.

Step 6

Clean skillet, if needed. Re-spray and bring to medium-high heat. Add beef, mushrooms, onion, and pepper. Sprinkle with remaining 1 tsp. cumin, 1 tsp. chili powder, 1/2 tsp. salt, and 1/8 tsp. each onion powder, garlic powder, and paprika. Cook, stir, and crumble until beef is fully cooked and veggies have softened, about 8 minutes.

Step 7

Using a slotted spoon, transfer skillet contents to the large bowl. Stir in corn and beans.

Step 8

Spread beef mixture over cauliflower layer in the baking pan, and smooth out the top. Top with tomatoes and remaining 1/2 cup cheese.

Step 9

Bake until entire dish is hot and cheese has melted, about 20 minutes.

Step 10

Let stand for 10 minutes before slicing.