Slice tops off peppers; remove seeds and membranes. Rinse well.

Bring a large pot of water to a boil. Add peppers; cook until crisp-tender, 15 minutes. Transfer to a broiler-safe baking dish; set aside.

Cook sausage and onions in a large, deep skillet over medium high heat until evenly brown. Reduce heat to medium. Stir in water, tomato soup, chili powder, garlic powder, salt, and pepper; bring to a low boil. Reduce heat to low; stir in 12 ounces cheese and simmer for 1 hour.

Meanwhile, preheat the oven to 350 degrees F (175 degrees C).

Prepare rice according to package instructions. Fluff with a fork, then stir into tomato mixture; simmer 30 minutes.

Spoon rice mixture into peppers.

Bake in the preheated oven for 30 minutes. Sprinkle remaining 3 ounces cheese on peppers; place under broiler until cheese melted and bubbly.