Preheat the oven to 350°F (177°C) and grease a 9×13-inch baking pan or line with parchment paper.
Mix the brown sugar, granulated sugar, cinnamon, and salt together in a medium bowl. Stir in the melted butter, then gently mix the flour using a fork. Keep the mixture as large crumbles, do not over-mix. Set aside.
Whisk the flour, baking soda, baking powder, and salt together. Set aside.
Using a handheld or stand mixer fitted with a paddle attachment, beat the butter and granulated sugar together on high speed until smooth and creamy, about 2 minutes. Add the eggs, sour cream, and the vanilla. Beat on medium-high speed until combined.
With the mixer on low speed, mix in the dry ingredients until smooth. Do not over-mix.
Spread the batter evenly into prepared baking pan. Top with crumb topping. Press the crumb topping tightly down into the cake so it sticks.
Bake for 45-55 minutes. The cake is done when a toothpick inserted in the center comes out clean.
Remove the cake from the oven and set on a wire rack. Allow to slightly cool for at least 30-45 minutes before cutting. Dust with confectioners’ sugar before slicing and serving if desired.
