Using a deep pot, preheat oil for frying to 350 degrees F.
Using a mixing bowl, stir together the cornmeal, flour, baking soda, and salt. Stir in the onion. In a small bowl, stir together the buttermilk and egg. Pour the buttermilk mixture into the dry ingredients and mix until blended. Drop the batter, 1 teaspoon at a time, into the oil. Dip the spoon in a glass of water after each hushpuppy is dropped in the oil. Fry until golden brown, turning the hushpuppies during the cooking process.