Preheat your oven to 350°F (175°C) and line an 8x8-inch baking dish with parchment paper.

In a medium bowl, whisk together the pumpkin puree, maple syrup, nut butter, egg (or a flax egg), and vanilla extract until smooth.

In another bowl, combine rolled oats, baking powder, pumpkin pie spice, and salt, then add to wet ingredients and stir until just combined.

Fold in any optional mix-ins like chocolate chips, nuts, or dried fruit.

Spread mixture into the prepared pan, smooth the top, and bake for 28-32 minutes until edges are golden.

Let cool in the pan for 30-40 minutes, then slice into 12 squares.