1. Preheat the oven to 350°F. Mist the inside of a 9-inch square light metal baking pan with the spray. (A dark metal or nonstick pan makes the crust very thick and dark.)
2. Whisk together the flour, cornmeal, baking powder, and salt in a small bowl and set aside. Beat together the butter and granulated sugar until light and fluffy in a large bowl with an electric mixer set to high speed. Scrape down the sides of the bowl with a rubber spatula. Add the eggs one at a time, beating well after each addition. Add the flour mixture and beat only until it disappears into the batter. Beat in the milk, vanilla, and lemon zest. Use a rubber spatula to gently fold in the berries.
3. Scrape the batter into the prepared baking pan and smooth the top. Sprinkle the sanding sugar over the batter, followed by the pecans. Bake until a tester inserted into the center of the cake comes out clean, about 40 minutes. Cool on a wire rack for at least 15 minutes before serving warm or at room temperature. The cooler the cake, the more neatly it will cut.
What else works? You can replace some or all of the blueberries with finely diced peaches.