In a large bowl, combine the yellow cornmeal, flour, sugar, baking powder, and salt.
In a separate bowl, whisk together the egg and buttermilk.
Pour the wet ingredients into the dry ingredients and mix until combined. The batter should be slightly thicker than pancake batter.
Add enough vegetable oil to coat the bottom of a cast-iron skillet or frying pan. Heat over medium heat, aiming for around 300°F. Test the oil with a small amount of batter; it should begin to sizzle.
Scoop about 2 tablespoons of batter into the skillet for each piece, leaving about 1 inch between them.
Cook until the edges are golden. The surface may bubble slightly, but the golden edges are the best cue that the first side is ready.
Flip each piece and gently press the center with a spatula to help the middle cook through.
Continue cooking until the second side is golden and the center is cooked through.
Adjust the burner as needed while frying to keep the oil from getting too hot or too cool. Add more oil between batches when necessary.
Transfer to a wire rack or paper towels to drain, then serve hot.