Preheat the oven to 350°F (175°C). Grease and lightly flour an 8x8-inch baking pan or line it with parchment paper.

In a medium bowl, whisk together the flour, baking powder, baking soda, salt, cinnamon, nutmeg, and ginger.

In a large bowl, cream the softened butter, granulated sugar, and brown sugar until light and fluffy.

Beat in the eggs one at a time, then mix in the pumpkin puree, sour cream, and vanilla extract until smooth.

Add the dry ingredients to the wet ingredients and stir just until combined. Do not overmix.

Pour the batter into the prepared pan and spread it evenly.

In a separate bowl, make the streusel by combining the flour, brown sugar, cinnamon, and salt. Cut in the cold butter using a pastry cutter or fork until the mixture forms coarse crumbs.

Sprinkle the streusel evenly over the batter.

Bake for 40 to 45 minutes, or until a toothpick inserted into the center comes out clean or with a few moist crumbs.

Let the coffee cake cool in the pan for at least 20 minutes before slicing and serving.