In a large mixing bowl, whisk together granulated sugar, brown sugar, cinnamon, salt and flour. Add melted butter and stir in until it all comes together. Fluff with a fork to make a mixture that resembles coarse crumbs. Set aside.
!for the cake:
Grease a 13"x9" baking pan. Set aside.
Preheat the oven to 350 degrees F.
In a large mixing bowl, cream together butter and sugar until light and fluffy, about 3 minutes.
Add eggs, one at a time, mixing well after each addition.
Mix in the vanilla.
In another mixing bowl, whisk together the dry ingredients (flour, baking soda, cinnamon and salt).
Add the dry ingredients to the butter mixture, alternating with sour cream.
Pour the batter into the prepared pan.
Sprinkle the topping over the batter.
Bake the cake for 35 to 45 minutes, or until a toothpick inserted in the center comes out clean.