Step 1

Preheat oven to 350°. Butter an 8x8" baking pan and line with parchment paper, leaving generous overhang on all sides; butter parchment. Whisk together 2 cups (250 g) all-purpose flour, ⅔ cup (packed; 133 g) light brown sugar, 1½ tsp. ground cinnamon, 1 tsp. Diamond Crystal or ½ tsp. Morton kosher salt, ½ tsp. freshly grated nutmeg, and ¼ tsp. ground cloves in a medium bowl. Add 12 Tbsp. (1½ sticks) unsalted butter, melted, slightly cooled, stirring with a spoon until most of the floury streaks are gone. Set streusel aside.

Step 2

Whisk 1 cup (125 g) all-purpose flour, 1 tsp. Diamond Crystal or ½ tsp. Morton kosher salt, 1 tsp. baking powder, ¼ tsp. baking soda, and ½ tsp. ground cinnamon in a large bowl.

Step 3

Whisk 2 large eggs, ¾ cup plus 2 Tbsp. pumpkin purée, ½ cup (100 g) granulated sugar, ¼ cup (packed; 50 g) light brown sugar, ½ cup (100 g) vegetable oil, 1 Tbsp. finely grated fresh ginger or ¼ tsp. ground ginger, and 1 tsp. vanilla extract in a medium bowl until smooth and creamy. Add pumpkin mixture to dry ingredients and gently stir until just combined (a few lumps are okay—it’s better not to overmix). Scrape batter into prepared pan and spread all the way to edges; smooth surface.

Step 4

Using your hands, squeeze reserved streusel into big clumps and evenly distribute over batter. (No need to press it down; it will all come together in the oven.)

Step 5

Bake cake until a thin knife inserted into the center comes out mostly clean (a few crumbs from the streusel are okay, but no batter), 35–40 minutes. Transfer pan to a wire rack and let cake cool until pan is no longer hot to the touch. Using parchment paper, lift cake out of pan and onto rack. Let cool completely.

Step 6

Just before serving, dust with powdered sugar and cut into a grid to make 9 or 12 pieces.Do ahead: Cake (without powdered sugar) can be baked 1 day ahead. Store tightly wrapped at room temperature.