#### **Step 1: Prepare the Bell Peppers**
Preheat oven to **375°F (190°C)**.
Cut the tops off the bell peppers and remove the seeds and membranes.
Lightly brush the outside with olive oil and place in a baking dish.
#### **Step 2: Cook the Filling**
Heat a large skillet over medium heat and add 1 tablespoon of olive oil.
Add chopped onion and garlic, sautéing for **2-3 minutes** until softened.
Stir in ground beef and cook until browned, breaking it apart as it cooks.
Drain excess fat, then season with salt, pepper, oregano, basil, and red pepper flakes.
Stir in diced tomatoes, marinara sauce, and cooked rice. Let simmer for **5 minutes**.
#### **Step 3: Stuff & Bake the Peppers**
Spoon the meat and rice mixture evenly into the hollowed-out bell peppers.
Cover with foil and bake for **30 minutes**.
Remove foil, sprinkle mozzarella and Parmesan cheese on top, and bake uncovered for another **10-15 minutes**, until cheese is melted and bubbly.
#### **Step 4: Serve & Enjoy**
Let the stuffed peppers cool slightly before serving.
Garnish with fresh basil or parsley if desired.