Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper for easy removal.
In a large mixing bowl, cream together the softened butter and brown sugar until the mixture is smooth and fluffy, about 2-3 minutes.
Add the pumpkin puree and large egg to the bowl, and whisk everything together until well combined and the mixture is slightly thickened.
In a separate bowl, sift together the flour, cinnamon, ginger, baking powder, and salt to evenly distribute the spices and leavening agents.
Gradually add the dry ingredients to the wet mixture, folding gently with a spatula until the dough just comes together and is moist but scoopable.
Using a tablespoon or cookie scoop, portion out the dough onto the prepared baking sheet, spacing each mound about 2 inches apart to allow for spreading.
Press each mound lightly with the back of a spoon or your fingertips to flatten just slightly—the cookies will spread as they bake.
Bake for 12-15 minutes, or until the edges are lightly golden and the cookies feel firm when gently touched.
Remove the cookies from the oven and let them cool on the baking sheet for 5 minutes; then transfer to a wire rack to cool completely.
Once cooled, enjoy these soft, spiced pumpkin cookies that carry a lovely aroma of cinnamon and ginger.