Cut the tempeh into 1/2-inch thick slabs. Arrange the slabs in a single layer in the air fryer basket, ensuring they do not touch each other.
While the tempeh is cooking, combine the coconut aminos, maple syrup, rice vinegar, minced garlic, ginger powder (if using), and cornstarch in a small saucepan.
Heat over medium-low and stir until the sauce thickens. Once the tempeh is done, transfer it to the saucepan and toss to coat.