Preheat and Prep: Preheat oven to 400°F. Grease a large baking sheet thoroughly with nonstick cooking spray.
Mix Dry Ingredients: In a medium bowl, whisk together flour, baking powder, salt, and cinnamon until evenly distributed.
Mix Wet Ingredients: In a large bowl, whisk melted butter and sugar until combined. Whisk in egg, vanilla, and applesauce until smooth.
Combine and Add Apples: Add dry ingredients to wet ingredients and stir just until combined. Gently fold in diced apples.
Portion and Bake: Scoop 1-tablespoon portions of batter onto prepared baking sheet, spacing 2 inches apart. Bake 10 minutes until puffed and set. Remove from oven and turn broiler to high.
Make Glaze: Whisk together powdered sugar and apple cider until smooth and thin enough to drip easily.
First Glaze and Broil: Brush about half the glaze over warm fritters, letting it drip down sides. Broil 2-4 minutes, rotating pan frequently, until glaze bubbles and caramelizes.
Final Glaze and Set: Remove from broiler and brush remaining glaze evenly over tops. Let sit 15 minutes for glaze to set before serving.