01 - Preheat oven to 350°F. Grease an 8x8-inch baking dish.
02 - In a medium bowl, whisk together flour, baking powder, baking soda, salt, cinnamon, nutmeg, and ginger.
03 - In a large bowl, mix pumpkin purée, brown sugar, eggs, oil, and vanilla until smooth.
04 - Gradually fold the dry ingredients into the wet mixture until just combined; do not overmix.
05 - Spread the batter evenly in the prepared baking dish.
06 - For the topping (optional), combine chopped nuts, brown sugar, and cinnamon; sprinkle over the batter.
07 - Bake for 30–35 minutes, or until a toothpick inserted in the center comes out clean.
08 - Cool slightly before serving warm, optionally topped with whipped cream or vanilla ice cream.