Preheat your oven to 350°F (175°C). I like to lightly butter a 9x9-inch pan and then line it with parchment paper. This simple step makes it easy to lift the cake out later and keeps the edges clean and perfect.

Whisk flour, leavening agents, salt, and spices in a bowl. That aroma is the first little hint of cozy fall magic! Set this dry mix aside while you prepare the wet ingredients.

In a large bowl, beat the granulated sugar, brown sugar, softened butter, and vegetable oil together until the mixture becomes light and fluffy. This creates a nice airy base for your batter.

Add the whole egg and mix it in well. Then add the extra egg yolk to give the cake a richer, velvety texture.

Stir in the pumpkin puree, sour cream, and vanilla extract until everything blends into a smooth, creamy batter. Take a moment here to appreciate that beautiful, silky mixture.

Switch to a spatula and gently fold the dry ingredients into the wet batter. This hands-on step helps keep the crumb tender and prevents overmixing.

Fill the prepared pan with batter and level the surface. I like to gently tap the pan on the counter to help settle the batter and get rid of any trapped air bubbles.

To make the crumb topping, mix the flour, salt, granulated sugar, and cinnamon in a bowl. Stir in the melted butter just until the mixture becomes crumbly. Stir in the chopped pecans for a lovely crunch.

Sprinkle the crumb topping evenly over the batter, aiming for small clusters instead of a fine dusting. These little clumps bake into pockets of buttery goodness.

Bake the cake for about 40 minutes, but start checking at 38 minutes. You want the crumb topping to turn a beautiful golden brown.

For the glaze, whisk the powdered sugar, heavy cream, and vanilla extract together until smooth. Drizzle it generously over the cooled cake and let it set for a few minutes. Then, slice and enjoy every delicious bite!