For the gluten-free flour blend: In a large bowl, whisk together the rice flour, tapioca flour, potato starch, xanthan gum and salt.
For the cornbread: Preheat the oven to 350 degrees F and grease or spray an 8- by 4-inch loaf pan with cooking spray. In a large bowl, combine the cornmeal, sugar, baking powder, baking soda, salt and 1 cup of the gluten-free flour blend. In a small bowl, whisk together the eggs, milk, oil and vinegar. Stir the liquid ingredients into the dry ingredients until just moistened; stir in the corn kernels.
Pour into the prepared loaf pan and bake until golden and a toothpick inserted near the center comes out clean, 40 to 45 minutes. Cool on a wire rack and serve.