In a spacious mixing bowl, blend together the yellow cornmeal, all-purpose flour, baking powder, and salt. In a separate container, whisk the egg, milk, and finely chopped onion until fully combined. Gradually incorporate the wet mixture into the dry ingredients, stirring just until everything is moistened and a thick batter forms.

Heat oil in a cast-iron Dutch oven or an electric skillet to a temperature of 365°F. Carefully drop tablespoonfuls of the batter into the hot oil, allowing them to fry until they achieve a rich, golden-brown hue, which should take about 2 to 2-1/2 minutes. Once fried, transfer the hush puppies to a plate lined with paper towels to drain any excess oil. Serve them warm for the best experience.