Thoroughly coat the diced apple in a small bowl with lemon juice to prevent browning. Set aside.
Preheat your oven to 375°F and line a baking sheet with parchment paper.
In a medium bowl, whisk together the flour, sugar, baking powder, cinnamon, nutmeg, and salt.
In a separate large bowl, whisk together the milk, egg, melted butter, and vanilla extract until combined.
Add the dry ingredients to the wet ingredients a little at a time and stir until just combined. The batter will be thick. Do not overmix!
Gently fold in the diced apples.
Spray the parchment paper on your prepared baking sheet lightly with a neutral cooking oil or cooking spray. Scoop the fritter batter using an ice cream scoop or large spoon and drop it onto the prepared baking sheet, shaping the fritters into rounds (about 2–3 inches wide). Lightly press them down for a more flattened shape.
Lightly spray the tops of the fritters with cooking spray, or brush them with a little melted butter or oil. This will help create a golden, crispy exterior while baking.
Bake for 25–30 minutes, or until the fritters are golden brown and crispy on the edges. Check after 20 minutes to ensure they don’t get too dark.
While the fritters are baking, whisk together the powdered sugar, milk, and vanilla extract in a small bowl until smooth. Adjust the consistency by adding more milk if needed.
Once the fritters are done baking, remove them from the oven and let them cool on the baking sheet for 5 minutes. Set a cooling rack over a baking sheet and transfer the fritters to the rack. Drizzle the glaze over the warm fritters and let it set slightly before serving.