Vegetable oil for greasing pan 1 ⅓ cup sugar, divided 3 cups blueberries (you can use any berry you like or mixed berries). 2 large eggs Finely grated zest of 1 large orange (you can sub lemon zest) ⅔ cup orange juice ⅔ cup olive oil (not extra virgin) or sunflower oil ½ cup regular or instant polenta 1 ¼ cups all-purpose flour 2 teaspoons baking powder ½ teaspoon salt Heat oven to 350 degrees. Grease and line base and sides of a 9-inch-square cake pan with baking parchment, and grease the parchment. Sprinkle 1/3 cup sugar over base of pan, and cover evenly with blueberries. In a large mixing bowl, combine eggs, 1 cup sugar and orange zest. Whisk until pale and thick. Add orange juice and oil, and whisk until blended. In a separate bowl, whisk together polenta, flour, baking powder and salt. Add flour mixture to egg mixture, whisking until smooth. Pour into prepared pan. Bake for about 45 to 55 minutes, until golden brown and springy to the touch, and a toothpick inserted near the center comes out clean. Cool cake on a rack for about 5 minutes. Carefully invert cake onto a serving plate, and slowly peel off parchment paper. Serve warm or at room temperature.