Thaw fish and cut into 1.5" strips.
Mix flour, baking powder and salt in medium bowl. Add extra flour to plate or shallow bowl for dredging.
Add in beer and whisk to until smooth.
Heat oil (1/2" deep) in pan on med-high heat.
Dredge fish pieces in flour, then in batter and place in hot oil.
Cook for 2-3 min, then flip and cook another 2-3 min. Remove from oil when batter is cooked and golden brown. Place on paper towel, top with extra salt and fresh lemon, if desired.
Serve immediately. Excellent with a dill-based tartar sauce, homemade "chips", coleslaw or mushy peas.