Step 1: Preheat the oven

Preheat the oven to 375°F (190°C). Set a 9-by-13-inch baking dish on your work surface.

Step 2: Prepare the peppers

Slice approximately ½ inch from the top of each bell pepper. Remove the stems from the tops if desired, and reserve the tops to use as lids.

Remove the cores and seeds from the peppers. If necessary, trim a very thin slice from the bottoms so they can stand upright without cutting a large opening. Poke about four small holes in the bottom of each pepper to allow juices to drain into the sauce.

Step 3: Make the tomato sauce base

Pour 2½ cups of the chunky tomato sauce into the baking dish. Add the sliced onion, beef broth, and red pepper flakes.

Stir gently and spread the mixture evenly across the bottom of the dish.

Step 4: Arrange the peppers

Stand the hollowed-out bell peppers upright in the tomato sauce, with their openings facing up.

Step 5: Mix the beef and rice filling

In a large bowl, combine the ground beef, cooked rice, shredded Parmesan-style cheese, 2 tablespoons of the remaining tomato sauce, ¼ cup parsley, minced garlic, salt, and black pepper.

Mix gently until the ingredients are evenly distributed. Avoid overworking the beef, which can make the filling dense.

Step 6: Stuff the peppers

Divide the filling evenly among the six peppers, spooning it in loosely rather than packing it down tightly.

Spread approximately 1 tablespoon of the remaining tomato sauce over the filling in each pepper. Reserve any sauce left over in the baking dish. Set the pepper tops back in place.

Step 7: Cover the baking dish

Lay a sheet of parchment paper loosely over the peppers, then cover the baking dish tightly with foil.

Place the dish on a rimmed baking sheet to catch any bubbling sauce.

Step 8: Bake covered

Bake the Beef and Rice Stuffed Bell Peppers for approximately 1 hour, until the peppers have started to soften.

Step 9: Finish baking uncovered

Carefully remove the foil and parchment paper, watching for hot steam. Return the dish to the oven and bake for another 20–30 minutes, until the peppers are tender and the beef filling is fully cooked.

Check the center of the filling in more than one pepper with a food thermometer. The ground beef must reach at least 160°F (71°C).

Step 10: Garnish and serve

Let the peppers rest for about 5 minutes. Sprinkle with the remaining tablespoon of parsley and spoon some of the warm tomato pan juices over each serving.