Add flour, cornstarch, sugar, salt, baking powder, baking soda, onion salt, paprika, and ground black pepper in a large bowl.
Stir to combine. Pour the club soda into the bowl with the dry ingredients.
As the club soda touches the dry ingredients the batter will begin to foam. Continue to stir.
Use a pair of kitchen tongs to dip the chicken tenders into the batter. Coat both sides of the tender.
Immediately (carefully) drop the coated chicken into the hot oil.
Fry the chicken tenders on each side for 2-3 minutes.
The batter will become a golden brown.
The tender will float to the top of the pot of hot oil.
Move each fried tender to a wire rack so the cooking oil will drain.
Serve.