Step 1

Bring a large skillet sprayed with nonstick spray to medium-high heat. Add cauliflower rice, onion, 1/8 tsp. garlic powder, and a dash each salt and pepper. Cook and stir until hot and softened, about 3 minutes. Transfer contents to a medium-large bowl. Cover to keep warm.

Step 2

Remove skillet from heat; clean, if needed. Re-spray and return to medium-high heat. Add beef, and season with remaining 1/8 tsp. garlic powder and dash each salt and pepper. Add mushrooms. Cook, stir, and crumble until beef is fully cooked and mushrooms have softened, about 5 minutes.

Step 3

Add cheese and mustard. Cook and stir until melted and well mixed, about 1 minute.

Step 4

Add beef mixture to the medium-large bowl, and top with tomato.