In a large mixing bowl, combine the rice flour, corn starch, salt, and baking powder. Mix well to ensure all the dry ingredients are evenly incorporated.
Gradually pour in the cold club soda while whisking the mixture continuously. Continue whisking until slightly lumpy. The batter should have a thin consistency similar to pancake batter.
Place the bowl of batter in the refrigerator to chill for about 10 minutes.
Heat a generous amount of canola oil in a deep fryer or large pot to 360°F. You'll need enough oil to submerge the food for frying.
While the batter is chilling and the oil is preheating, pat the prepared fish and vegetables dry with paper towels to remove excess moisture.
Once the oil is hot, dip the prepared fish or vegetables into the chilled tempura batter, coating them evenly.
Carefully place the battered food into the hot oil, a few pieces at a time, depending on the size of your fryer or pot.
Fry the battered food for about 1-2 minutes, or until they are golden brown and crispy. Use a slotted spoon or tongs to gently turn the pieces halfway through cooking for even browning.
Once cooked, remove the fried food from the oil and transfer them to a plate lined with paper towels to drain any excess oil. Serve immediately and enjoy!
