Pour oil into a large pot, about 3 inches deep, and heat the oil to 350º–375ºF. Note: If you don’t have a deep fat thermometer, use an instant-read meat thermometer, provided the stem is long enough! You’ll want to regularly check the oil’s temperature and ensure you stay at a consistent 350ºF–375ºF.
Pat the cod pieces dry and season lightly with salt. Set aside.
Combine the flour, chili powder, salt, baking powder, paprika, cayenne powder, and garlic powder in a bowl.
Pour in the beer and whisk until completely smooth and free of lumps. The batter will be thicker than cream but still a tad runny.
Place all of the cod pieces in the batter and toss to combine.
Using tongs, lift a piece of cod from the batter and lightly shake off any drippy excess batter. Slowly drop it into the hot oil. Fry 4–6 pieces at a time, depending on the width of your pot. Be sure not to overcrowd the pot! Cook for 3–4 minutes until golden brown all over. Use a slotted spoon to transfer a paper towel-lined plate. Continue frying in batches, checking and adjusting the temperature periodically.