Preheat the oven to 400 degrees F (200 degrees C). Lightly grease a 9-inch round cake pan.
Whisk flour, cornmeal, sugar, baking powder, and salt together in a large bowl.
Add milk, vegetable oil, and egg.
Whisk until well combined.
Pour batter into the prepared pan.
Bake in the preheated oven until a toothpick inserted into the center of the pan comes out clean, 20 to 25 minutes.