Heat oil in a large saucepan or deep fryer to 375 degrees. Combine cornmeal, chopped onion, flour baking powder, baking soda and salt. Make a well in center of dry ingredients; add well beaten eggs and buttermilk at the same time. Mix until blended. Form into small cakes, about 1 tablespoon each. Drop hush puppies into deep fryer, a few at a time.
Fry 3 to 4 minutes, until well browned. Turn with fork or tongs as they float to the surface. Remove with slotted spoon and drain on paper towels. Makes 2 dozen.