Saute onions and garlic until softened; set aside. Combine meatloaf ingredients; mix well. Press into bottom and up sides of a 13 x 9 inch baking dish. Bake 30 minutes or until no longer pink and juices run clear. Drain carefully and blot with paper towels. Spread salsa over meatloaf and sprinkle with 1 cup cheese.
Combine mashed potatoes and drained corn. Keep warm or reheat in micro wave. Spread over cooked meatloaf. Sprinkle with remaining 1 cup cheese and dust with chili powder. Return to oven for 5 to 10 minutes or until cheese melts.