Preheat the oven to 350°.
In a separate bowl, whisk together the dry ingredients.
2 1/4 c. all-purpose flour, 1 1/4 tsp. baking powder, 1 tsp. baking soda, 1/2 c. brown sugar, 1 tsp. salt, 2 1/2 tsp. pumpkin pie spice, 1 tsp. ground cinnamon
In a large mixing bowl, beat the eggs until fluffy.
2 large eggs
Add the pumpkin, oil, buttermilk, and vanilla and mix well.
1 1/2 c. pumpkin puree (NOT pumpkin pie mix), 1/2 c. canola or vegetable oil, 3/4 c. buttermilk or greek yogurt, 2 tsp. vanilla extract
Gently mix the dry ingredients into the wet ingredients until combined.
Spread the batter into a well-greased 9 x 13" baking pan.
Sprinkle the crumb topping evenly over the top and lightly press it onto the cake.
Bake at 350° for 28 - 32 minutes or until a toothpick comes out with only a few crumbs.
Cool for a few minutes and serve. Or let it cool, cover, and store at room temperature for up to two days. Refrigerate for up to a week. Or freeze it, in an airtight container, for later.