In a large bowl, whisk the pumpkin puree, melted butter, brown sugar and vanilla until smooth.
Add the flour, protein powder, pumpkin pie spice, baking powder, baking soda and salt, and stir until a soft dough forms. Cover and chill for 30 minutes.
Meanwhile, blend the cottage cheese, egg yolk, sugar, cornstarch and vanilla until completely smooth and silky. Preheat the oven to 350°F and line 2 baking sheets with parchment paper.
Scoop the dough into 16 balls, about 2 tablespoons each, and place them 2 inches apart. Flatten each ball to 1/2 inch thick and press a wide, shallow well into the center with the back of a spoon.
Spoon about 2 teaspoons of the cheesecake mixture into each well. Drag a toothpick through the filling and slightly into the dough to create a swirl, then dust lightly with cinnamon.
Bake for 13 to 15 minutes, until the cookies are set and the cheesecake swirl no longer looks wet.
Cool on the baking sheets for 10 minutes, then move to a wire rack. Chill for 30 minutes for a firmer cheesecake swirl, and store in the fridge.