Preheat the oven to 350 degrees F. Grease 8"x8" square baking pan. Set aside.
In a medium mixing bowl, whisk together flour, soda, baking powder and salt. Set aside.
In a large mixing bowl of a stand mixer, cream butter for 30 seconds. Gradually add sugar and cream until fluffy and light.
Add eggs, one at a time, beating well after each addition.
Add vanilla and mix well.
Add dry ingredients alternating with sour cream.
Mix well. Batter will be thick.
Spread the batter in prepared pan.
!to make the topping:
In a medium mixing bowl, stir together both sugars, molasses, cinnamon and salt. Add melted butter and stir. Add flour and stir until it all comes together. It will looks like a thick dough.
Breaking it into pieces with your fingers, sprinkle the topping over the cake.
Bake the cake for 30 to 35 minutes, or until the toothpick inserted in the center comes out clean. Cool in pan.