Preheat the oven to 400 deg.
Heat a large skillet on medium heat; add the ground beef and chopped onion. Cook, stirring occasionally, until meat is fully cooked with some brown bits.
Stir in 1 c of the tomato sauce, 1 c water, sugar, soy sauce, garlic powder, parsley, salt and mustard powder. Increase the heat and bring to a boil. Stir in minute rice, then cover with the lid and take it off the heat. Let stand for 5 min.
While you wait, cut peppers lengthwise in half and remove the stem and seeds.
Mix remaining tomato sauce and a sprinkle more garlic powder; pour it into the bottom of a 13 X 9 inch pan. Place the peppers in the bottom of the pan, like little boats.
Spoon meat mixture into the peppers and cover with foil.
Bake for 35-40 min. Spoon the sauce over the peppers before serving.