Onions Au Gratin

8 c. sliced onions (approx. 3 lbs)
1/2 c. water
3 1/2 c. sharp cheddar grated
1/2-2/3 c. flour
1 tsp baking powder
1 tsp salt
1/4 tsp pepper
4 T butter

Cook onions in water until tender (approx 15 min). Drain well. Add 3 c. cheese and remaining ingredients. Put into a 2 qt casserole dish and sprinkle with remaining cheese. Bake at 350 for 35 min.