In 2-quart casserole crumble ground beef.
Add onion; micro-cook, covered, till meat is brown, about 5 minutes, stirring several times to break up meat.
Drain off excess fat.
Stir in enchilada sauce and tomato sauce.
Micro-cook, covered, 5 minutes, stirring once.
Drain beans; stir beans, 7 cup of the corn chips, and 3/4 cup of the cheese into meat.
Micro-cook, covered, 6 minutes, stirring once.
Stir, then spread sour cream over top; sprinkle remaining chips and cheese over top.
Cook just till sour cream is hot, 30 to 45 seconds.