Arrange a rack in the middle of the oven and heat the oven to 375°F.

Cut the tops off of 6 medium bell peppers. Use a spoon to scoop out and discard the seeds and white membrane. Finely chop the tops, avoiding and discarding the seeds and stem (1 to 1 ½ cups). If needed, trim a little bit off the bottom of the bell pepper so that it is stable when standing up.

Dice 1 medium yellow onion (about 1 ½ cups). Mince 2 garlic cloves. Grate 4 ounces low-moisture mozzarella or Monterey Jack cheese on the large holes of a box grater if needed (about 1 cup), or measure out 1 cup store-bought shredded. Pick the leaves from 8 fresh parsley sprigs and coarsely chop until you have ¼ cup.

Heat 1 tablespoon olive oil in a large cast iron or stainless steel skillet over medium-high heat until shimmering. Add the onion, bell pepper tops, 1 teaspoon kosher salt, and ½ teaspoon black pepper. Cook until soft and beginning to brown, 4 to 5 minutes. Add the garlic and 1 tablespoon dried Italian seasoning, and cook until fragrant, about 30 seconds.

Add 1 pound mild Italian sausage, ground beef, or ground turkey. Cook, breaking up the meat into smaller pieces with a wooden spoon, until browned and cooked through, 4 to 5 minutes. Add ½ cup low-sodium chicken broth and scrape up any browned bits from the bottom of the pan. Add 1 (14.5-ounce) can diced tomatoes and their juices, 1 cup cooked white or brown rice, and the parsley. Stir to combine and cook until the liquid is mostly evaporated, about 3 to 5 minutes.

Remove the pan from the heat. Add ½ cup of the cheese and stir to combine. Taste and season with more kosher salt or black pepper if needed.

Evenly divide the filling among the peppers (about ¾ cup filling per bell pepper). Arrange the peppers, cut-side up, in an 11x7-inch or 9x13-inch baking dish. Pour in enough water to just cover the bottom of the baking dish (½ to ¾ cup). Cover the baking dish tightly with aluminum foil.

Bake until the peppers are tender and the filling is heated through, about 35 minutes. Uncover and divide the remaining ½ cup cheese evenly over the peppers. Return to the oven and bake uncovered until the cheese is melted and browned, 8 to 10 minutes. Garnish with more chopped fresh parsley leaves if desired.