Preheat oven to 350°F (175°C). Line a 12-cup muffin tin with paper liners or lightly grease.
In a blender or food processor, blend cottage cheese until completely smooth. Add pumpkin puree, egg yolks, maple syrup, and vanilla. Blend until combined.
In a separate bowl, whisk together oat flour, protein powder, baking powder, baking soda, salt, and pumpkin pie spice.
Pour the pumpkin-cottage cheese mixture into the dry ingredients. Stir gently until just combined.
In a clean bowl, beat the egg whites until soft peaks form. Gently fold them into the batter in 2–3 additions, being careful not to deflate the air.
Divide the batter into the prepared muffin cups, filling nearly to the top. Bake for 18–20 minutes, or until tops are golden and just set.
Let muffins cool for 5–10 minutes before removing from pan. Serve warm or at room temperature.