In a small bowl, combine chili powder, cumin, garlic powder, paprika, salt, pepper, oregano and red pepper flakes.
In a large skillet over medium heat, brown ground beef until just cooked through, about 7 to 10 minutes, breaking up any clumps with the back of a wooden spoon. Add spice mixture and sauté until well combined. Remove from heat.
Preheat oven to 400F and line a large baking try with parchment paper or aluminum foil. Arrange mini peppers in a single layer, cut-side up but very close together.
Sprinkle with ground beef mixture and shredded cheese (make sure every mini pepper gets a little meat and cheese!). Bake 5 to 10 minutes, until cheese is melty.
Remove from oven and top with chopped tomatoes and any other desired toppings. Serve immediately.
Notes
Storage Information
Store the leftovers in a covered container in the fridge for up to 5 days. Re-heat in a warm oven.