Heat the oven to 350°F (175°C) and line a 12-cup muffin pan.
Blend pumpkin puree, cottage cheese, eggs, maple syrup, and vanilla until mostly smooth.
Stir in oat flour, protein powder if using, baking powder, baking soda, pumpkin pie spice, cinnamon, and salt. Mix just until combined.
Divide the batter between the muffin cups. Bake for about 18–22 minutes, or until a toothpick inserted near the center comes out clean.
Let the muffins rest in the pan for 5–10 minutes before transferring them to a rack.