Preheat your air fryer to 400°F (200°C) to ensure a hot cooking environment for the fish.
Pat the fresh sardines thoroughly dry with paper towels; removing moisture is the secret to achieving a golden, crispy skin.
In a medium mixing bowl, gently toss the sardines with the extra virgin olive oil, sea salt, and black pepper until each fish is evenly coated.
Arrange the sardines in a single layer in the air fryer basket, making sure they do not overlap so the air can circulate freely.
Air fry for 8 to 10 minutes, carefully flipping the fish halfway through the cooking time until the exterior is crisp and the flesh is opaque.
While the sardines are cooking, prepare the gremolata by finely chopping the fresh parsley and combining it with the minced garlic and lemon zest in a small bowl.
Place the fresh baby arugula on a serving plate as a vibrant, peppery base for the fish.
Transfer the hot sardines onto the arugula, drizzle with fresh lemon juice, and garnish generously with the lemon-herb gremolata.