Preheat oven to 350°F. Spray a 9x13-inch baking dish with nonstick spray.
Wash peppers, slice lengthwise in half, and remove seeds and membranes.
Place pepper halves cut-side up in a microwave-safe casserole dish with ¼ cup water.
Cover and microwave 5 to 6 minutes, or until peppers are just starting to soften. Carefully drain any excess water.
While the peppers cook, brown the ground beef in a large skillet over medium heat until cooked through, breaking it up as it cooks.
Drain excess grease if needed.
Add taco seasoning and ¾ cup water to the skillet. Stir and simmer according to the recipe or packet directions, until the mixture thickens.
Remove skillet from heat. Stir in sour cream, salsa, and 1 cup of the shredded cheddar cheese until fully combined.
Arrange peppers in the dish and fill each half generously with the beef mixture.
Sprinkle with the remaining ½ cup cheddar cheese.
Bake 20 to 30 minutes, or until peppers are soft, heated through, and the cheese is melted.
Serve warm and top with your favorite taco toppings.
