01 - Preheat oven to 350°F. Grease and line a 9x13-inch baking pan with parchment paper.
02 - In a medium bowl, whisk together all-purpose flour, baking powder, baking soda, salt, cinnamon, nutmeg, ginger, and cloves until evenly blended.
03 - In a large bowl, whisk together granulated sugar, light brown sugar, pumpkin puree, vegetable oil, eggs, and vanilla extract until the mixture is smooth and fully combined.
04 - Gradually fold the dry ingredients into the wet mixture using a spatula, mixing until just incorporated. Take care not to overmix.
05 - Gently stir in the chopped pecans to distribute them evenly throughout the batter.
06 - Pour the batter into the prepared pan, smoothing the top. Bake for 28 to 32 minutes, or until a toothpick inserted in the center comes out clean. Cool the cake completely in the pan on a wire rack.
07 - Melt unsalted butter in a saucepan over medium heat. Add light brown sugar and whole milk, stirring until the sugar dissolves. Bring to a gentle boil and cook for 1 minute, then remove from heat and allow to cool for 10 minutes.
08 - Whisk in sifted powdered sugar and vanilla extract until the frosting is smooth and spreadable.
09 - Spread the butterscotch frosting evenly over the fully cooled cake.
10 - Sprinkle with chopped pecans, slice, and serve.