Heat oven to 375°F.
Combine ground beef, bread crumbs, onion, ketchup, mustard and salt in medium bowl. Mix well. Press mixture in bottom and up the sides of ungreased 9-inch pie pan. Bake for 15 minutes.
Cook bacon until crisp. Drain on paper towel. Cool and crumble.
Combine water, butter and garlic salt in medium saucepan. Bring to a boil. Remove from heat. Add milk. Using fork, stir in potato flakes. Stir in 1/2 cup cheese.
Remove partially baked beef crust from oven. Pour off any drippings. Spoon potato mixture evenly into crust. Return to oven. Bake an additional 10 to 15 minutes or until beef is thoroughly cooked and potatoes are heated.
Remove pie from oven. Top with tomato, remaining 1/2 cup cheese, and crumbled bacon. Return to oven. Bake an additional 5 minutes or until cheese is melted. Remove from oven.
Top with green onions. Let stand 10 minutes.
Cut into wedges to serve.