Add flour, garlic powder, onion powder, paprika, and a pinch of salt to a medium bowl. Whisk in the beer until smooth. Let the batter rest for 10 minutes while prepping the fish. The foam should subside entirely. Place 3/4 cup of flour in a shallow bowl. Set aside.
In a Dutch oven or saucepan, bring oil to 365°F. This recipe works best if the fish is completely submerged in oil. Meanwhile, cut the cod filet into equal portions, pat dry with a paper towel, and season with salt and pepper.
Dredge cod filets in flour, and then submerge in the beer batter. Remove, let excess drip off, and immediately transfer to the hot oil.
Deep fry each piece for 4-5 minutes, flipping halfway through if not completely submerged in oil. Remove fish with a slotted spoon or spider strainer and place on a paper towel-lined plate to drain for 5 minutes before serving. Serve with lemon wedges, ketchup, tartar sauce, and fries of choice.