Heat oven to 350° F. Spray baking dish with nonstick cooking spray.

In large skillet, cook onion and ground beef until cooked through. Drain, if necessary.

Stir in chili powder and cumin. Stir in pinto beans and diced tomatoes; set aside.

In small bowl, combine sour cream, flour and garlic powder.

Place six tortillas in bottom of baking dish, overlapping as needed. Top tortillas with beef mixture and sour cream mixture. Top with 10 ounces enchilada sauce. Repeat layers.

Bake 35-40 minutes.

Sprinkle shredded cheese and green onion over casserole. Bake 5 minutes, or until cheese melts.