Directions
Preheat oven to 350 degrees. Brush an 8-inch square pan with oil; dust with flour, tapping out excess. Whisk together flour, almonds, polenta, baking powder, and 1/2 teaspoon salt. Beat eggs, sugar, and zest with a mixer on high speed until pale and fluffy. Reduce speed to low; slowly add oil. Beat in flour mixture in 3 additions, alternating with milk, beginning and ending with flour. Spoon batter into pan; scatter 1 cup grapes over top. Bake for 15 minutes. Scatter remaining cup grapes over cake. Bake until cake is golden and a toothpick inserted into the center comes out clean, 25 to 27 minutes more. Let cool in pan on a wire rack for 15 minutes. Turn out, and cut into squares.