Mix sugar, butter and chili sauce. Add salt, pepper, and chili powder to taste (optional). Toss mixture gently with the sliced onions until well coated. Pour all into a large casserole dish. Cover and bake at 350 degrees for 35 minutes, then stir in the rice. Bake 10 more minutes, covered, then stir well. Sprinkle a generous amount of grated Parmesan over the top. Return to oven and bake uncovered for 3 to 5 minutes to brown the cheese.