Take a cookie sheet and line it with parchment paper or paper towels put a drying rack on top.
Cut onions into rings of the size you desire add to a bag and add corn starch to the bag. ( I used about 1/4 C) shake to cover rings.
Whisk wet ingredients, egg, milk with vinegar, tonic, in a bowl.
Mix dry ingredients rice flour, cornstarch, cornmeal, paprika, onion powder, garlic powder, salt, sugar (optional), in a bowl.
Add dry ingredients to wet ingredients a little at a time starting until you have a thick batter.
Heat oil in a skillet or deep pan to 350 degrees using a thermometer if you have one.
Remove rings from the bag and shake excess cornstarch and dip into batter and fry in batches (do not crowd) adding to sheet in the oven as they are done (sprinkle each batch with salt while hot).
Be careful frying. If it seems to be getting too hot keep decreasing the temp on your stove.The oil will start evaporating as you go.I ended up turning the burner down to a 5. If you need to add more oil, just remember that you need to wait to let it come up to frying temperature before frying your next batch or you will end up having oily greasy rings.