Combine beer and cilantro in a bowl. Stir and then add the prawn. Let it stay for at least 3 hours.
Make the basting sauce by combining butter, salt, and garlic powder. Mix well.
Heat-up the grill. Put the marinated prawn on the grill and then continue to grill one side for 4 minutes. Baste the opposite side with the butter mixture. Turn the prawn over to grill the other side. Do not forget to apply the basting sauce.
Transfer the grilled prawn in a serving plate. Serve with lemon wedges.
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