Chef John's Savory Stuffed Peppers

Gather all necessary components for the recipe.\nCombine rice and water in a saucepan, then heat it over high intensity until the mixture reaches boiling point. Gradually decrease the heat to a lower setting, cover the saucepan, and let it simmer until the rice is tender and all liquid has been absorbed, typically taking 20 to 25 minutes. Set the cooked rice aside for later use.\nPreheat your oven to a temperature of 375 degrees Fahrenheit (190 degrees Celsius) for the duration of the recipe.\nPrepare the sauce by heating olive oil in a pan over medium heat until the onion begins to soften, approximately 5 minutes. Transfer half of the cooked onion to a large container and set it aside for future use.\nCombine marinara sauce, beef broth, balsamic vinegar, and red pepper flakes in the same pan with the cooked onion; cook and stir for 1 minute to allow the flavors to meld.\nTransfer the sauce mixture into a 9x13-inch baking dish and set it aside for later use.\nCombine ground beef, Italian sausage, diced tomatoes, Italian parsley, garlic, salt, black pepper, and cayenne pepper in the bowl with reserved onions; mix well to combine all ingredients. Stir in cooked rice and Parmigiano Reggiano cheese to add texture and flavor.\nFill green bell pepper halves with the beef and sausage mixture, ensuring they are evenly filled.\nPosition the stuffed green bell pepper halves in the baking dish over tomato sauce; sprinkle with remaining Parmigiano Reggiano cheese, cover the baking dish with aluminum foil, and bake in the preheated oven for 45 minutes.\nRemove the aluminum foil and continue baking until the meat is no longer pink, the green peppers are tender, and the cheese is browned on top, typically taking an additional 20 to 25 minutes. Serve and enjoy your finished dish!