Preheat the air fryer to 400°F for 3 minutes.
Pat shrimp dry with paper towels and place in a medium bowl.
Toss shrimp with oil, lemon juice, lemon zest, minced garlic (if using), salt, and cracked black pepper until evenly coated.
Arrange shrimp in a single layer in the air fryer basket with space between pieces; work in batches if necessary.
Cook at 400°F for 4 minutes, shake basket or flip shrimp, then cook an additional 3–4 minutes until shrimp are opaque and form a loose C with light browning at edges.
Transfer shrimp to a bowl, toss with melted butter if using, and grate a little extra lemon zest over the top before serving.