US Janet, I use a batter just for fish and for onion rings. (Sometimes for fish, I just dredge in
a mix of cornmeal and flour, like you.)

My batter recipe is:

2 1/4 C flour
1 tsp. Baking powder
1/2 tsp. Salt
20-24 oz. room temp beer or enough to make the desired consistency

This makes enough batter for one large onion.

N.