Preheat oven to 350 degrees F. Spray a half baking sheet with nonstick cooking spray. In a mixing bowl, combine eggs, Truvia, applesauce, collagen, protein powder, and pumpkin puree until fully incorporated.
Slowly add the flour but continue stirring to avoid lumps. Mix until well combined. Add the cinnamon, pumpkin pie spice, baking powder, baking soda, and salt and mix until well combined.
Pour the batter into prepared baking sheet and spread in an even layer. Bake for 25-30 minutes, or until set and let cool completely.
For the frosting, cream together cream cheese and protein powder in a mixing bowl until fluffy. Add vanilla, salt, milk, and powdered sugar; mix until smooth.