Place the cold butter in a small saucepan over medium-high heat. Let it melt, then continue cooking, swirling the pan occasionally without stirring. Watch for the milk solids to separate and begin browning—this takes 5-7 minutes. You'll smell something rich and nutty, and you'll see golden-brown flecks settling on the bottom. The moment it smells toasted and looks amber-colored, remove from heat and let it cool slightly. This is where the magic happens—those browned milk solids add depth that regular butter can't deliver.

Pour the slightly-cooled brown butter into a small bowl with the powdered sugar. Whisk together until completely smooth and glossy, about 1-2 minutes. Add the vanilla extract and mix. If your glaze looks too thick (it should pour slightly when warmed), add the milk one teaspoon at a time until you reach the right consistency. The glaze will thicken as it cools, so aim for something that drizzles rather than dollops. Set this aside while you prep the fritter batter.

Set your air fryer to 400°F and let it preheat for 3-4 minutes. This step is non-negotiable. A properly preheated basket ensures immediate browning on contact, creating that crispy exterior. Don't rush this—patience here pays off in texture.

In a medium mixing bowl, whisk together the flour, granulated sugar, baking powder, salt, cinnamon, and optional nutmeg. Use a whisk rather than a fork—whisking aerates the flour and distributes the leavening agents evenly. This prevents dense, heavy fritters. Whisk for about 30 seconds until everything looks combined and you don't see any streaks of cinnamon.

Make a well in the center of your dry ingredients. Add the room-temperature eggs, milk, vanilla extract, and fresh lemon juice directly into that well. Using a spatula or wooden spoon, stir gently until everything is just combined—about 20-30 seconds. The batter will look slightly lumpy. That's perfect. Overmixing develops gluten, making fritters tough instead of tender. Fold in the diced apples gently until distributed throughout.

Line the preheated air fryer basket with parchment paper or air fryer basket liners, cutting to fit snugly at the bottom without overlapping the sides. Brush or spray lightly with oil—just enough so the fritters won't stick, not so much that they become greasy. A light coating is your goal.

Carefully drop approximately ¼ cup of batter onto the lined basket for each fritter. Depending on your air fryer size, you'll likely fit 2-3 fritters per batch. Don't overcrowd—they need air circulation to crisp properly. Lightly brush or spray the tops with oil using a pastry brush. This ensures even browning on both sides.

Set the air fryer to 400°F for 4-5 minutes. Watch through the window if your model has one. You're looking for the tops to turn light golden-brown. At the 4-minute mark, check one fritter by gently shaking the basket—they should feel set on top.

Carefully flip each fritter using tongs or a small spatula. Be gentle—they're delicate at this stage. Lightly brush or spray the now-exposed side with oil. Return to 400°F for another 4-5 minutes until both sides are deep golden-brown. The fritters should look caramelized and feel firm when you press gently with a fork (they'll still be slightly soft inside).

Transfer fritters to a cooling rack immediately—don't leave them in the basket. Place a piece of parchment beneath the rack to catch glaze drippings (trust me, this saves cleanup). While the fritters are still warm (crucial for glaze adhesion), drizzle the brown butter glaze generously over each one. The warmth allows the glaze to soak slightly into the cake while also setting into a glossy coating. Work quickly because the glaze thickens as it cools.

These taste best within 15-20 minutes of completion while they're still warm and the glaze is set but the cake is tender. Serve alongside a hot beverage or as part of a larger breakfast spread.