Preheat your oven to 350°F and line a small loaf pan with parchment paper to prevent sticking.
In a medium mixing bowl, whisk together the oat flour, vanilla protein powder, pumpkin pie spice, baking powder, and sea salt until well combined.
In a separate bowl, stir together the pumpkin puree, liquid egg whites, non-fat Greek yogurt, and vanilla extract until the mixture is smooth.
Gradually fold the dry ingredients into the wet pumpkin mixture using a spatula until just combined.
Transfer the batter into the prepared loaf pan and spread it into an even layer.
In a small dish, mix the almond butter and maple syrup together, then dollop the mixture over the top of the pumpkin batter.
Use a toothpick or the tip of a knife to gently swirl the almond butter mixture into the batter to create a marbled effect.
Bake for 22 to 25 minutes, or until the edges are golden and a toothpick inserted into the center comes out clean.
Remove from the oven and let the bars cool completely in the pan before slicing into squares.