In a large bowl, stir 2 cups flour, baking powder and baking soda until blended. Set aside.
Beat granulated sugar, softened butter and vanilla in large bowl with mixer until light and fluffy. Add eggs, 1 at a time, beating well after each addition. Beat in flour mixture alternately with sour cream.
In a separate bowl, combine 2 Tablespoons flour, cold butter, brown sugar and cinnamon.
Pour half of the cake batter into a prepared pan - we used a loaf pan but a bundt pan for ease would be more traditional.
Spoon half of the brown sugar-cinnamon crumble overtop of the cake batter, and then repeat. You will have two alternating layers of cake batter-crumble.
Bake 45 to 50 min. or until toothpick inserted near center comes out clean. Cool cake in pan 10 min. Loosen cake from sides of pan with knife. Invert cake onto wire rack; gently remove pan. Cool cake completely.
Wait until the coffee cake has mostly cooled (or completely cooled) before drizzling overtop. You can use a piping bag or a spoon - I kind of think the imperfection is part of the charm in comfort foods like coffee cake, and fussing with a piping bag feels out of place with this recipe.