Heat the oil in a large skillet over medium heat. Use an oven-safe skillet if you'll be broiling cheese at the end!
Add the onion, bell peppers, and mushrooms and cook until soft, about 5 minutes.
Stir in the tomato paste and garlic and cook until the garlic is softened & fragrant, about 1 minute.
Add the ground turkey and use a wooden spoon to break up the meat, cooking until no longer pink - about 5 minutes.
Turn up the heat to high, then add the cauliflower rice. Sauté until the cauliflower is just tender, about 3 minutes.
Stir in the diced tomatoes, and season with oregano, salt, and pepper.
Sprinkle with cheese, if using, then transfer to the oven with the broiler on. Broil for 3 minutes or until the cheese is just melted and starting to turn golden.
Garnish with fresh chopped parsley & serve warm. Enjoy! Tastes even better the next day.