Spread the shrimp and asparagus evenly on a sheet pan.
In a small bowl, mix melted butter, minced garlic, lemon juice, and lemon zest. Brush the butter mixture onto the asparagus and shrimp.
Season everything with lemon pepper seasoning, garlic powder, crushed red pepper flakes (if using), salt, and black pepper.
Bake for about 8 minutes or until the asparagus is slightly tender and the shrimp are pink. The asparagus is cooked but a bit crisp at this stage, remove the shrimp and cook the asparagus 3-5 minutes longer if you want it more tender. If the asparagus starts to get too dark, cover it with tinfoil to finish cooking. It may take a little longer if you use thicker asparagus pieces.
Remove the pan from the oven and then top the shrimp with chopped parsley before serving.
Notes
The cooking times may vary depending on the size of shrimp and asparagus, so keep a close eye on them. The shrimp should be slightly pink and no longer opaque when done. Do not overcook the shrimp or they will become rubbery.