Step 1: Preheat your oven to 375°F (190°C). Lightly grease a 9×13 inch baking dish.
Step 2: Prepare the bell peppers by washing them, cutting them in half lengthwise, and removing all seeds and membranes. Place them cut-side up in the prepared baking dish.
Step 3: In a large skillet, heat the olive oil over medium-high heat. Add the ground beef and cook, breaking it up with a spoon, until browned. Drain any excess fat.
Step 4: Add the diced onion to the skillet with the ground beef and cook until softened, about 5 minutes. Stir in the minced garlic and keto-friendly taco seasoning, cooking for another minute until fragrant.
Step 5: Stir in the drained diced tomatoes and water or beef broth. Bring the mixture to a simmer and cook for 3-5 minutes, allowing the flavors to meld and the liquid to reduce slightly. Remove from heat.
Step 6: Spoon the taco meat filling evenly into each bell pepper half in the baking dish. Top each stuffed pepper generously with shredded cheese.
Step 7: Bake for 25-30 minutes, or until the bell peppers are tender-crisp and the cheese is melted and bubbly. If you prefer softer peppers, you can cover the dish with foil for the first 15-20 minutes, then uncover for the last 10 minutes to brown the cheese.
Step 8: Carefully remove from the oven and let rest for a few minutes before serving. Garnish with your favorite keto-friendly toppings like sour cream, avocado, or fresh cilantro.