How to Make It
Preheat oven to 350°F. Grease a 13- x 9-inch baking pan with butter; set aside.
Combine 2 1/2 cups flour, baking powder, and salt in a small bowl. Set aside.
In the bowl of a mixer, cream together butter and sugar until lightened, about 3 minutes. Add eggs one at a time, waiting for each to incorporate before adding the next. Beat for another 2 minutes. Add vanilla extract and sour cream and stir until fully combined. Add dry ingredients and mix until there are no pockets of flour.
Coat the chopped strawberries in the additional 1 tablespoon of flour. Gently fold flour-coated strawberries into cake batter. Evenly spread cake batter in prepared baking pan.
In mixer, cream together butter and sugar for Cake Topping. Add flour, cinnamon, and salt. Beat until the mixture resembles coarse wet sand. Sprinkle Cake topping evenly across Cake batter. Bake until lightly golden on the surface and a toothpick inserted comes out clean, about 40 minutes. Allow to cool completely before cutting into squares and serving with whipped cream and fresh strawberries.