Preheat your oven to 400 degrees fahrenheit and grease a 9-inch square baking dish or cast-iron skillet.
In a large bowl, whisk together the gluten free all-purpose flour, yellow cornmeal, granulated sugar, baking powder, and salt.
In a separate medium bowl, whisk the buttermilk, eggs, and melted butter until smooth.
Pour the wet ingredients into the dry ingredients and stir gently until just combined. Avoid overmixing.
Pour the batter into the prepared baking dish and smooth the top with a spatula.
Bake for 20 to 25 minutes, or until the top is golden brown and a toothpick inserted into the center comes out clean. Let cool slightly before slicing.