Preheat oven to 350°F (175°C). Line a baking sheet with parchment paper.
Whisk dry ingredients in a large bowl: rolled oats, oat flour, baking powder, cinnamon, and salt.
Blend cottage cheese until completely smooth.
In a separate bowl, whisk wet ingredients: egg, blended cottage cheese, maple syrup, oil, and vanilla.
Pour wet into dry and fold just until no dry spots remain.
Fold in the finely diced apple until evenly distributed.
Scoop 12 cookies onto the prepared sheet; flatten slightly (they won’t spread much).
Bake 12 to 14 minutes, until edges are lightly golden and centers are set.
Cool on the pan 5 minutes, then transfer to a wire rack to finish cooling.
Optional glaze: whisk powdered sugar with maple syrup and drizzle over cooled cookies.
Store covered up to 3 days at room temp, up to 6 days refrigerated, or freeze up to 2 months.
