Preheat your grill to medium-high heat (425° F).
Tear three pieces of Reynolds Wrap® Heavy Duty Foil: 16–18 inch pieces are enough for this meal.
Add the shrimp and trimmed asparagus to the center of the foil packets. Divide the shrimp and asparagus evenly.
Make the Lemon Garlic Butter sauce: Soften the butter in the microwave for 15–20 seconds so that it is mixable, but not bubbly hot. Mix all of the spices and herbs in the butter then divide the sauce evenly between the three packets.
Seal the foil packets for 15 minutes: Bring up the long sides of the foil, so the ends meet over the food. Double-fold the ends, leaving room for the heat to circulate inside. Double-fold the two short ends of the packet.
Grill the packet: Use a long spatula to pick up the packet.
Let it rest for 1–2 minutes.
Top with more lemon juice, red pepper flakes, and/or parsley before serving.