With an adult’s help, preheat oven to 400°F. Coat an 8 x 8-inch baking pan with cooking spray.
Measure the flour, cornmeal, sugar, baking powder, and salt, and toss the ingredients into a medium mixing bowl. Stir the ingredients with a large spoon until all are well mixed. Form a well in the batter’s center.
Crack an egg into a small bowl and beat with a fork. Pour the beaten egg into the middle of the well, and then add the milk and vegetable oil. Stir the batter until the ingredients are mixed. (It’s OK if some little bits of flour are still visible. You don’t want to overbeat the batter.)
Transfer the batter to the prepared pan. Smooth out the top using a small plastic knife.
Ask an adult for help putting the pan in the oven. Bake for about 25 minutes. Remove from oven when a toothpick inserted into the center comes out clean and when the top of the cornbread is golden brown. Let cool in the pan for about an hour. Cut and serve.