Preheat the oven to 350°F. Grease and line a 9x5 loaf pan with parchment paper.
In a medium bowl, whisk together flour, baking powder, baking soda, sugar, ginger, nutmeg, salt, and cinnamon until combined.
In a separate large bowl, mix together pumpkin puree, oil, eggs, and vanilla until combined.
Pour the wet ingredients into the bowl with the dry ingredients and mix until just combined, being careful not to overmix.
Fold in the chopped walnuts (if using). Pour batter into prepared loaf pan and bake for 50-60 minutes or until a toothpick inserted into the center comes out clean.
Let cool in pan for 10 minutes then remove from pan and transfer to cooling rack. Allow to cool completely before slicing.