Crafting this cake is as straightforward as a leisurely stroll through an autumn park. Here’s how you can make it:

1. Preheat your oven to 350°F (175°C) and grease a 9-inch square baking pan.
2. In a medium bowl, whisk together flour, baking powder, baking soda, salt, cinnamon, nutmeg, and ginger. Set aside.
3. In a large bowl, cream together the softened butter and sugar until light and fluffy, about 3-4 minutes.
4. Add eggs one at a time, beating well after each addition. Stir in pumpkin puree, vanilla extract, and sour cream until well combined.
5. Gradually add the dry ingredients to the wet ingredients, mixing just until combined. Be careful not to overmix, as this can make the cake dense.
6. Pour the batter into the prepared baking pan, smoothing the top with a spatula.
7. For the crumble topping, mix together flour, granulated sugar, brown sugar, and cinnamon. Stir in melted butter until the mixture resembles coarse crumbs.
8. Sprinkle the crumble topping evenly over the batter.
9. Bake for 35-40 minutes, or until a toothpick inserted into the center comes out clean.
10. Allow the cake to cool in the pan for at least 15 minutes before slicing and serving.

There’s something therapeutic about watching the cake rise and brown, filling the house with that unmistakable smell of home.