Preheat the oven to 350°F (177°C).
Slice each bell pepper in half lengthwise and remove the seeds and membranes.
Arrange the peppers cut-side up on a lightly greased baking dish or baking sheet.
Cover with foil and bake for 15 minutes until slightly tender.
Carefully drain any liquid that collects inside the peppers.
Meanwhile, heat a large skillet over medium-high heat and cook the ground beef until browned.
Drain excess grease if necessary.
Add the diced onion and cook for about 5 minutes until softened.
Stir in the taco seasoning, tomato paste, and minced garlic. Cook for 1 minute until fragrant.
Pour in the water and bring the mixture to a gentle simmer.
Add the black beans and diced tomatoes with green chilies.
Simmer for 5 minutes until the filling thickens.
Spoon the taco mixture evenly into each baked pepper half.
Sprinkle generously with shredded Mexican cheese.
Return the Taco Stuffed Peppers to the oven and bake for another 15 minutes, or until the cheese is melted and bubbly.
Serve warm with your favorite taco toppings.