Preheat oven to 350F
Place 6 halves of bell peppers on baking pan and bake in the oven for 10-15 minutes.
In a mean time, use a large sautéed pan over medium high heat, add unsalted butter followed by white onion (and fresh garlic, if you opt for it instead of garlic powder). Cook onion for a minute then add mushroom and continue cooking for another minute.
Add beef tenderloin, stir occasionally and season with Cajun seasoning, garlic powder. Adjust seasoning with salt and pepper according to your taste. Sauté for 3 to 5 minutes just enough to fully cook tenderloin. It’s important to not over cook the beef.
Take baked bell peppers out of the oven and put 1 slice of provolone on the bottom of each pepper half.
Add the steak mixture to the peppers, then top them up with the rest of provolone slices.
Then return the bell peppers now stuffed with beef tenderloin and provolone to the oven. Bake for 10 minutes or until the cheese melted completely.
Garnish with chopped parsley and sprinkle Cajun seasoning on top. Serve hot immediately.