Cut peppers in half, remove the seeds, place in a large glass baking dish and set aside. Preheat oven to 400 degrees.
Heat the oil in a large skillet over med/high. Add onion, sea salt and pepper, and cook for 5. Add the mushrooms and cook for another 2 minutes.
Add the turkey, garlic powder, oregano, paprika, red pepper flakes.
Cook while breaking up the meat for 5-7 minutes until no longer pink.
Add in tomato paste and stir. Add the crushed tomatoes and simmer over low heat for 10 minutes, stirring occasionally. Adjust seasonings to taste. Add cooked rice, spinach, and stir to combine.
Spoon the mixture into bell peppers.
Top each pepper with a little bit of cheese. Pour the chicken stock into the bottom of the baking dish and cover the dish lightly with foil. Bake for about 25 minutes.