In a medium bowl, combine 1/2 cup all-purpose flour, 1/4 cup granulated sugar, 2 tablespoons brown sugar, and 1/2 teaspoon ground cinnamon. Add 4 tablespoons cold, cubed unsalted butter and cut it in with a pastry blender or your fingers until the mixture resembles coarse crumbs. Chill the crumble topping in the refrigerator while you prepare the cake batter.

Preheat your oven to 350°F (175°C). Grease and flour a 9-inch round cake pan, ensuring it is thoroughly coated to prevent sticking.

In a large bowl, whisk together 1.5 cups all-purpose flour, 1 teaspoon baking powder, 1/2 teaspoon baking soda, 1 teaspoon ground cinnamon, 1/2 teaspoon ground nutmeg, 1/2 teaspoon ground ginger, and 1/4 teaspoon salt until well combined.

In a separate bowl, whisk together 1 cup canned pumpkin puree, 3/4 cup granulated sugar, 1/4 cup brown sugar, 2 large eggs, 1/2 cup vegetable oil, and 1 teaspoon vanilla extract until the mixture is smooth and evenly combined.

Gradually add the dry ingredients to the wet ingredients, mixing with a spatula or spoon until just combined. Be careful not to overmix the batter, as this can lead to a dry cake.

Pour the cake batter evenly into the prepared 9-inch round cake pan. Evenly sprinkle the chilled crumble topping over the top of the cake batter.

Bake for 40-50 minutes, or until a wooden skewer or toothpick inserted into the center of the cake comes out clean, indicating it is fully cooked.

Allow the cake to cool in the pan for 10 minutes before carefully transferring it to a wire rack to cool completely. This helps the cake set and prevents it from breaking when removed from the pan.