1. Preheat your oven to 350 F (175 C). Lightly grease a 9×13 inch baking pan or line it with parchment paper, leaving an overhang on the sides for easy lifting later.

2. In a large mixing bowl, using an electric mixer, cream together the softened butter and 1 1/2 cups granulated sugar until the mixture is light and fluffy, about 2-3 minutes.

3. Beat in the egg and vanilla extract until well combined. Then, add the pumpkin puree and mix until just incorporated. Do not overmix at this stage; a few streaks are fine.

4. In a separate medium bowl, whisk together the all-purpose flour, baking soda, salt, ground cinnamon, ground nutmeg, and ground cloves. Ensure all the dry ingredients are evenly distributed.

5. Gradually add the dry ingredient mixture to the wet ingredients, mixing on low speed until just combined. Be careful not to overmix the dough, as this can lead to tough bars. The dough will be thick and soft.

6. Evenly press the dough into your prepared 9×13 inch baking pan. In a small bowl, combine the 1/4 cup granulated sugar and 1 tablespoon ground cinnamon for the topping. Sprinkle this cinnamon-sugar mixture generously over the top of the dough.

7. Bake for 25-30 minutes, or until the edges are lightly golden brown and a toothpick inserted into the center comes out with moist crumbs, but not wet batter. The center should look set.

8. Allow the bars to cool in the pan on a wire rack for at least 20 minutes before slicing into squares. This cooling time helps them set and makes for cleaner cuts.