Prep the Apples: In a medium bowl, combine the diced apples with the lemon juice, tossing to coat. Set aside.
Mix the Dry Ingredients: In another medium bowl, whisk together the gluten-free flour, granulated sugar, cornstarch, baking powder, cinnamon, nutmeg, and salt until well combined. Set aside.
Prepare the Wet Ingredients: In a large bowl, whisk together the eggs, milk, and vanilla extract until smooth.
Combine the Batter: Gradually add the dry ingredient mixture to the wet ingredients, stirring until a thick, smooth batter forms. Fold in the prepared apples, mixing until evenly distributed.
Heat the Oil: In a deep, heavy-bottomed pan or Dutch oven, add the vegetable oil. It should be about 3-4 inches in depth. Heat the vegetable oil to 370-375°F (190°C). It should take about 10 minutes to heat up the oil. Use a candy thermometer to keep an eye on the oil temperature as you’ll want it to stay constant throughout deep frying the fritters.
Fry the Fritters: Working in batches, carefully drop large spoonfuls (I use a large cookie scoop/portion scoop) of the batter into the hot oil, forming misshapen circles. After dropping into the oil, I like to use the spoon to lightly punch down the dough to flatten it. This helps prevent the fritter from being a round circle which tends to be harder to cook through. Fry each fritter for about 2-3 minutes on each side, or until golden brown and cooked through. Flip halfway through to ensure even frying. I usually can deep fry 3-4 fritters at a time. You don’t want to do too many at a time, otherwise the oil temperature can easily drop too much and if the fritters are too crowded they don’t brown as easily.
Drain and Cool: Use a slotted spoon or spider spatula to transfer the fritters to a wire rack to cool slightly and keep them crisp. I usually line a baking sheet with paper towels and then place the wire rack on top to help with easy cleanup. Repeat the frying and draining process with the remaining fritter batter until its all used up.
Make the Glaze: In a small bowl, whisk together the powdered sugar, vanilla extract, and apple cider (or water) until smooth.
Glaze the Fritters: Drizzle the glaze over the warm fritters or dip each fritter in the glaze, allowing any excess to drip off. Serve warm.