Preheat oven to 400 degrees F. Spray an 8-inch square baking dish (glass is recommended) with non-stick cooking spray.

In a large bowl, whisk the flour, cornmeal, baking powder, baking soda and salt until combined; set aside.

In a food processor or blender, process the sugar, thawed corn kernels and buttermilk until combined, about 5 seconds. Add the eggs and process until well combined (corn lumps will remain), about 5 seconds longer.

Using a rubber spatula, make a well in the center of the dry ingredients; pour the wet ingredients into the well. Fold the dry ingredients into wet, giving the mixture only a few turns to barely combine; add the melted butter and continue folding until the dry ingredients are just moistened (do not overmix!)

Pour the batter into the prepared baking dish and smooth the surface with a rubber spatula. Bake until deep golden brown and a toothpick inserted in the center comes out clean, 20 to 30 minutes. Cool on a wire rack for 10 minutes, then invert cornbread onto wire rack, turn right side up and continue to cool until warm, about 10 minutes longer. Cut into pieces and serve.