Spray a 9x9 square baking dish with cooking spray. I like to line it with sheets of parchment with long ends, so I can lift it out after baking for easy cutting. This is optional.
Put the flour, sugar, baking powder, salt, and spices in the bowl of a food processor fitted with the blade. Pulse to combine everything well.
Cut the cold butter into pieces and add them to the processor. Process by pulsing repeatedly until the butter has been incorporated and the mixture has a crumbly texture. About 20-30 pulses, more or less.
Remove a cup of the dry mixture and put in a small bowl. Toss with 1/4 teaspoon of cinnamon and set aside for the topping.
Whisk the eggs, pumpkin, and sour cream together in a large mixing bowl until smooth. Add in the flour mixture and stir just until everything is mixed, but don't over beat it.
Spread the batter in the prepared pan, evening it out with a spatula. Sprinkle the reserved crumbs evenly over the top.
Bake for approximately 55-60 minutes, or until risen in the center and a toothpick comes out clean.