In a large saucepan, cook ground beef with onions and garlic, stirring frequently, until browned and pour off drippings.
Add tomato sauce and chili powder and bring to a boil.
Reduce heat and simmer uncovered for 8-10 minutes or until most of liquid is absorbed, stirring occasionally.
Meanwhile, heat oil in a 10-inch nonstick ovenproof skillet over medium-high heat until sizzling.
Add potatoes, pressing into one layer.
Cook 5 minutes or until bottom is golden brown.
Turn with large spatula and continue cooking 4 to 5 minutes or until bottom of potatoes are golden brown, reducing heat if potatoes are browning too quickly.
Don't worry if potatoes break apart when you turn them and just pat them back together with the spatula.
Spoon ground beef mixture over potatoes and top with tomatoes, chilies and cheese.
Broil 3 to 4 inches from broiler 2-3 minutes or until cheese is melted.