Slice tops off 6 bell peppers chef's knife cutting board. Pull seeds ribs inside spoon clean. Large pot boil water add 1 tsp salt. Dunk peppers 2 minutes soft flexible tongs. Ice bath cold water 2 minutes stop cook. Stand cut side up baking dish.
All-Clad skillet medium heat. Add 1 lb ground beef break spatula crumble 5 minutes brown drain fat spoon. Add 1 diced onion 2 minced garlic stir 3 minutes soft fragrant. Pour 15 oz tomato sauce 1 tsp Italian ½ tsp salt ¼ tsp pepper. Fold 1 cup rice simmer 5 minutes thick.
Preheat oven 375°F. Spoon beef rice filling peppers mound tops full. Pack gentle spoon no gaps. Sprinkle ¼ cup cheddar each pepper top crusty. Foil tent loose baking dish 20 minutes steam tender.
Foil off bake 5 minutes cheese bubble gold. Rest 5 minutes peppers stand firm. Garnish parsley serve hot slice clean.