Preheat oven to 350Grease an 8 inch square or round baking pan with butter or baking spray.

In a large bowl, whisk together flour, sugar, cinnamon, ginger, allspice, baking powder, and baking soda. Set aside.

Beat butter until light and fluffy, about 2-3 minutes. Add egg, and beat until combined. Add molasses and buttermilk, and stir until combined.

Add flour mixture, about a third at a time, until flour is well incorporated and there are no remaining dry bits.

Make the topping by stirring together the brown sugar, salt, and cinnamon in a separate bowl. Pour melted butter over sugar and combine with a fork. Add flour, and mix with fork until combined.

Pour cake batter into prepared baking pan. Crumble the topping evenly over the batter.

Bake 35-40 minutes, or until a toothpick inserted in the middle of the cake comes out clean.

Let cool and enjoy!