Preheat the oven to 425ºF. If using an air fryer, see instructions below.
In a large bowl, whisk together the flour, cornstarch, sugar, baking powder, spices, and salt. In a separate small bowl, whisk together the milk, egg, lemon juice, and vanilla extract.
Add the cold butter cubes to the bowl of dry ingredients and cut them in using a pastry cutter or your hands. Gently squish the butter into the flour until it looks like sand, with only small chunks of butter remaining.
Pour the wet ingredients into the dry and stir together with a rubber spatula. Fold in the apple chunks last. The batter will be quite thick. Allow to sit for 2 minutes to absorb.
Prepare a baking sheet with parchment paper. Use a large greased ice cream scoop or ¼ cup measuring cup to scoop the batter onto the baking sheet. You should have enough for 8 fritters. Use the back of the scoop to gently press the batter into discs. Spray lightly with cooking spray for colour. Bake for 12-13 minutes, then broil on high for 1-2 minutes until golden, keeping an eye on the fritters. While the fritters bake, stir together the glaze ingredients in a small bowl.
Allow the fritters to cool for 2 minutes until you can handle them, then flip each fritter upside down, dunk in the glaze, then flip back up and rest on a wire rack above a baking sheet for the glaze to drip. Allow the glaze to set for 3-5 minutes, then enjoy warm!