Preheat oven to 375 degrees F.

Slice the peppers lengthwise in half, then use a small knife to gently cut out most of the ribs and shake out the seeds. Lightly coat a casserole dish or a rimmed baking sheet with cooking spray, then place peppers in it with the cut side facing up. Bake for 15 minutes.

While the peppers start baking, add the beef and onion to a large skillet set over medium-high heat. Cook, stirring to crumble the meat, for 2-3 minutes, then stir in the garlic and taco seasoning. Continue to cook until the onions are tender and the meat is mostly browned.

Stir in the black beans and tomatoes, then simmer for 4-5 minutes more, until the liquid is mostly cooked off. Remove skillet from the heat.

After the peppers have baked for 15 minutes, remove the pan from the oven and carefully spoon the beef mixture into each one. Top with cheese, then return peppers to the oven. Bake for another 15 minutes.

Garnish the baked peppers with fresh cilantro leaves and top with avocado, sour cream, salsa, or other traditional taco toppings as desired. Enjoy!