Spray a medium, heavy-bottomed pan with cooking spray (or add a tbsp of olive oil) and heat on medium high heat.
Add the diced onion, pepper, garlic, and celery. Cook, stirring occasionally for about 5 minutes, or until they soft and translucent.
Meanwhile, microwave chopped cauliflower for 2 minutes until mostly cooked.
Add cauliflower to the pot and sprinkle in the cumin and chili powder; cook for an additional 2-3 minutes.
Add tomatoes, tomato paste, and BBQ sauce. Stir and reduce heat to low. Cook until everything is mixed together evenly and heated through.
Serve with toasted bread or buns of your choice!