Transfer cake batter to prepared baking dish spread batter evenly with rubber spatula or offset spatula. Add flour mixture in 3 additions, beating just until incorporated after each addition. Add sour cream and vanilla extract and beat just until blended. Add eggs 1 at a time, beating until well blended after each addition. Add sugar and beat until light and fluffy. Using electric mixer, beat room-temperature butter in large bowl until smooth. Sift flour, baking soda, baking powder, and salt into medium bowl. Butter 13 x 9 x 2-inch glass baking dish. Position rack in center of oven and preheat to 350☏. Add flour and toss with fork until moist clumps form (topping mixture will look slightly wet). Add warm melted butter and stir to blend. Mix both sugars, cinnamon, and salt in medium bowl and whisk to blend.
