Preheat the oven to 350°F (175°C) and prepare a baking pan.
In a large mixing bowl, combine pumpkin purée, brown sugar, maple syrup, and melted butter.
Add eggs and vanilla extract to the pumpkin mixture, whisking until fully incorporated.
In a separate bowl, whisk together the dry ingredients: flour, baking powder, salt, cinnamon, and nutmeg.
Gradually fold the dry mixture into the wet ingredients until just combined.
If desired, fold in the chopped nuts to the batter.
Pour the batter into the prepared baking pan, spreading it evenly.
Bake for 25–30 minutes, or until a toothpick inserted into the center comes out clean.
Allow the blondies to cool in the pan for at least 10 minutes before transferring to a wire rack to cool completely.
Cut into squares and serve warm or at room temperature.