Preheat your oven to 375 degrees Fahrenheit (190 degrees Celsius). Lightly grease a baking dish.
Cut the bell peppers in half lengthwise and remove the seeds and membranes. Place the pepper halves cut-side up in the prepared baking dish.
Heat the olive oil in a large skillet over medium heat. Add the chopped onion and cook until soft, about 5 minutes. Add the minced garlic and cook for 1 minute more.
Add the ground beef to the skillet. Cook, breaking it up with a spoon, until browned. Drain any excess grease.
Stir in the taco seasoning and water. Bring the mixture to a simmer and cook until the liquid reduces slightly, about 5 minutes.
Remove the skillet from the heat. Stir in the softened cream cheese and half of the shredded cheese until melted and combined into the meat mixture.
Spoon the meat filling evenly into the hollowed-out bell pepper halves.
Top each stuffed pepper half with the remaining shredded cheese.
Bake for 25 to 30 minutes, or until the peppers are tender and the cheese is melted and bubbly.
Remove from the oven. Top with sour cream and your preferred keto toppings before serving.
Notes
You can substitute ground turkey or ground chicken for the ground beef.
For extra flavor, add 1/4 cup of finely chopped jalapeño with the onions.
If you prefer a softer pepper, you can microwave the pepper halves for 2 minutes before stuffing them.