Preheat oven to 400 degrees F.
Heat olive oil in a large skillet over medium heat. Sauté onion until softened, about 3-4 minutes. Add the ground beef and garlic, breaking the meat apart with apart using a utensil. Cook until it is no longer pink. Drain any excess grease.
Stir in chili powder, cumin, salt, pepper, fire-roasted tomatoes, and salsa. Continue to cook on medium heat for about 10 minutes, stirring frequently, until most of the liquid has been absorbed. Remove from heat and stir in the black beans.
Slice the bell peppers down the middle lengthwise and remove the ribs and seeds. Leave the stem intact; this will help hold the taco filling inside of the peppers. Arrange the peppers into a 9 x 13 dish.
Spoon the taco filling into each pepper, making sure to press the filling down into the peppers. Divide the cheese evenly and sprinkle over top each pepper.
Bake for 25 minutes until peppers are fork tender and cheese is hot and bubbly.
