1. Preheat oven to 350°F (175°C) and line a 9×9-inch pan with parchment paper.

2. In a bowl whisk flour, baking powder, baking soda, salt, cinnamon, nutmeg, cloves, and allspice.

3. In a separate bowl beat pumpkin puree, oil, brown sugar, granulated sugar, eggs, vanilla, and buttermilk until smooth.

4. Gently fold dry ingredients into wet ingredients until just combined.

5. In another bowl mix brown sugar, flour, and cinnamon for topping, then stir in melted butter until coarse crumbs form.

6. Pour batter into prepared pan and sprinkle crumb topping evenly over it.

7. Bake for 35–40 minutes until a toothpick inserted in center comes out clean.

8. Allow cake to cool in pan 15 minutes, then transfer to a rack and cool 10–15 minutes before slicing.

9. Serve warm or at room temperature with coffee or a drizzle of glaze.

10. Store leftovers in an airtight container at room temperature up to three days or freeze slices up to two months.