1. Preheat oven to 375 degrees. Brush a 9-by-9-inch baking pan with butter. Sprinkle with flour; shake to coat. Tap out excess; set aside.

2. In the bowl of an electric mixer fitted with the paddle attachment, cream butter, 3/4 cup sugar, and honey until fluffy, about 3 minutes. Add eggs one at a time. Beat until incorporated; do not overbeat. Add sour cream; mix to combine. Whisk together flour, cornmeal, baking powder, and salt. Add dry ingredients to batter; mix to combine. Scrape sides of bowl with a spatula; mix again.

3. Spread batter in prepared pan. Brush with water; sprinkle with remaining sugar. Bake until cake springs back when gently pressed in the center, about 30 minutes. Cool slightly on a wire rack. Whip cream. Cut cake into squares; split. Fill with cream and berries.