Step 1: Reduce the Apple Cider: Pour 2 cups of apple cider into a small saucepan. Bring to a simmer over medium-high heat, then reduce heat to medium-low. Simmer gently until the cider has reduced to about 1/2 cup (120ml), approximately 15-20 minutes. Set aside to cool completely.
Step 2: Whisk Dry Ingredients: In a large bowl, whisk together the all-purpose flour, 1/2 cup granulated sugar, light brown sugar, baking powder, 1 teaspoon ground cinnamon, nutmeg, allspice, ground ginger, baking soda, and salt.
Step 3: Combine Wet Ingredients: In a separate medium bowl, whisk together the 4 tablespoons melted butter, egg, vanilla extract, and the cooled, reduced apple cider.
Step 4: Mix Dough: Pour the wet ingredients into the dry ingredients. Mix with a spatula or wooden spoon until just combined. Do not overmix; a few lumps are fine. Cover the bowl with plastic wrap and refrigerate for at least 30 minutes, or up to 1 hour, to make the dough easier to handle.
Step 5: Shape the Donuts: Lightly flour a clean surface. Turn the chilled dough out onto the floured surface and gently pat or roll it to about 1/2 inch (1.25 cm) thickness. Use a 3-inch donut cutter or a round cookie cutter (and a smaller one for the center) to cut out donut shapes. Re-roll scraps gently to cut more donuts.
Step 6: Preheat Air Fryer: Preheat your air fryer to 350°F (175°C) for 3-5 minutes. Lightly spray the air fryer basket with non-stick spray.
Step 7: Air Fry Donuts: Place the donuts in a single layer in the air fryer basket, ensuring they don't touch. You will need to work in batches. Air fry for 4-6 minutes, flipping halfway through, until golden brown and cooked through. Cooking times may vary, so keep an eye on them. Transfer cooked donuts to a wire rack to cool slightly.
Step 8: Prepare Coating: While the donuts are still warm, prepare the cinnamon-sugar coating. In a shallow bowl, combine the remaining 1/2 cup granulated sugar and 1 tablespoon ground cinnamon.
Step 9: Coat Donuts: Brush each warm donut lightly with the 2 tablespoons of melted butter, then dredge immediately in the cinnamon-sugar mixture, ensuring it's fully coated. Serve warm and enjoy your delicious Air Fryer Spiced Apple Cider Donuts!