Prepare Peppers for Steaming: Slice the bell peppers in half from stem to bottom and remove all seeds and white membranes. Arrange the four pepper halves, cut-surface-down, in a microwave-safe baking dish large enough to hold them comfortably. Pour the 2/3 cup of water around (not inside) the peppers in the dish.

Steam Peppers: Lay a sheet of parchment paper over the peppers, then tightly cover the entire dish with microwave-safe plastic wrap. Microwave on high power for 3-5 minutes, or just until the peppers begin to soften slightly but still hold their shape. With extreme caution to avoid steam burns when uncovering, carefully remove the plastic wrap and parchment paper. Drain all water from the baking dish and reposition the peppers with the cut side facing upwards. Set aside.

Brown Beef and Sauté Aromatics: While the peppers are pre-cooking, warm the oil in a large skillet or frying pan over medium-high heat. Once the oil is hot, add the ground beef. Cook, breaking it apart with a sturdy spoon or spatula, until it is fully browned, which should take approximately 5 minutes. Add the chopped red onion, chopped mushrooms, and minced garlic to the skillet with the beef. Continue to cook, stirring frequently, for another 4-6 minutes, until the vegetables have softened and the mixture is fragrant.

Spice the Filling: Stir in the ground cumin, chili powder, smoked paprika, ground chipotle chili, salt, and ground cinnamon. Stir constantly and cook for about 30 seconds more, until the aroma of the spices is released and they are well combined with the beef and vegetables.

Add Tomato Puree: Remove the skillet from the heat source. Stir in the canned tomato puree until it is thoroughly integrated into the beef mixture.

Stuff and Finish Peppers: Divide the savory meat mixture evenly among the four steamed pepper halves. Sprinkle the shredded sharp cheddar cheese equally over the filling in each pepper scoop.

Melt Cheese and Serve: Return the baking dish containing the stuffed peppers to the microwave. Heat them, uncovered, on high power for 2-4 minutes, or until the cheese is completely melted, bubbly, and the peppers are heated through and tender. Serve immediately while warm.