Prep oven. Position a rack in the center of your oven and preheat to 350°F/177°C. Grease and line a 9x9 baking pan with parchment paper.
Combine dry ingredients. In a large bowl, whisk together the flour, baking powder, baking soda, and salt. Set aside. 1 ¼ cups (150 g) all purpose flour ¼ teaspoon salt ¼ teaspoon baking powder ¼ teaspoon baking soda
Cream butter and sugar. In a large mixing bowl with an electric mixer cream together butter and 1 cup + 2 tablespoons sugar (225 g) on medium high speed until light and fluffy, about 2 minutes. ½ cup (1 sticks,113 g) unsalted butter
Add eggs and vanilla. beat in the eggs one at a time. Add in vanilla and beat to combine. Scrape down the bowl as needed. 2 large eggs 2 teaspoons vanilla extract
Alternate dry mixture and sour cream. Stir in the flour mixture and sour cream alternately to butter-sugar-egg mixture, beginning and ending with the flour mixture until uniformly incorporated- do not overmix. ½ cup (113 g) sour cream
Assemble cake. Spread cake batter into the prepared pan. Sprinkle the top of the cake with remaining 3 Tablespoons granulated sugar (38 g) for a thick crunchy coating.
Bake. Bake in a preheated 350°F oven for approximately 30 minutes, until top is golden brown and when the cake is done when a toothpick or skewer inserted in the center comes out clean or with a few moist crumbs. Cool in the pan on a wire rack before cutting and serving.