Prep the pan and oven: Heat the oven to 350°F (175°C). Grease a 9x13-inch baking pan and line it with parchment, leaving a slight overhang for easy lifting.

Make the streusel: In a bowl, mix 1 1/2 cups flour, 3/4 cup brown sugar, 1/3 cup granulated sugar, 1 1/2 teaspoons cinnamon, and a pinch of salt. Stir in 1/2 cup melted unsalted butter until large crumbs form. If you like, mix in 1/2 cup chopped pecans. Set aside.

Whisk dry ingredients for the cake: In a large bowl, whisk 2 cups flour, 1 cup granulated sugar, 1 teaspoon baking powder, 1 teaspoon baking soda, 1 teaspoon cinnamon, 1/2 teaspoon nutmeg, and 1/2 teaspoon kosher salt.

Combine wet ingredients: In a separate bowl, whisk 1 cup pumpkin puree, 2 large eggs, 1/2 cup oil, 3/4 cup milk, and 2 teaspoons vanilla until smooth.

Bring the batter together: Pour the wet ingredients into the dry. Stir gently with a spatula until just combined. A few small lumps are fine—don’t overmix.

Assemble: Spread the batter evenly in the prepared pan. Sprinkle the streusel evenly over the top, breaking up any very large clumps for even coverage.

Bake: Bake for 30–38 minutes, or until the center springs back and a toothpick comes out clean or with a few moist crumbs. Start checking at 30 minutes.

Cool: Place the pan on a rack and cool at least 20 minutes. For clean slices, cool to room temperature.

Optional glaze: Whisk 3/4 cup powdered sugar with 1–2 tablespoons milk until pourable. Drizzle over the cooled cake.

Serve: Cut into squares and serve slightly warm or at room temperature with coffee or tea.