Great question. Yes, you can definitely use a square or rectangular pan! An 8×8-inch square pan or a 9×7-inch rectangular pan would work perfectly, as long as it’s at least 2 inches deep to match the volume of the original 9-inch round pan. You’ll just need to arrange the pineapple slices to fit the corners, and the baking time should remain the same at 45 minutes total. The caramelized topping will look beautiful in any shape!