Mix both sugars, cinnamon, and salt in medium mixing bowl. Add the warm melted butter and stir to blend.
Add flour and mix with a fork until moist clumps form. Set aside.
Preheat the oven to 350 degrees.
Grease 13″ x 9″ baking pan.
Mix together the flour, baking soda, baking powder, and salt then set aside.
Beat the softened butter in large bowl until light.
Add sugar and beat until light and fluffy.
Add eggs 1 at a time, beating until well blended after each addition.
Add buttermilk and vanilla, beat just until blended.
Add flour mixture in 3 additions, beating just until blended after each addition.
Transfer cake batter to prepared baking pan; spreading it evenly over the pan.
Hand squeeze small handfuls of topping together to form small clumps. Drop topping clumps evenly over cake batter, covering with a thick layer of topping.
Bake 1 hour or until tester comes out clean and topping is deep golden brown and a little crisp.
Cool cake in dish on rack at least 30 minutes.
Dust with powdered sugar and cut into squares to serve.
I worked with this recipe.