In a large bowl, combine the cornmeal, flour, baking powder, salt, and cayenne pepper. Whisk to mix.
In a medium bowl, whisk together the egg and buttermilk. Stir the wet mixture into the dry mixture, just until combined. Then, fold in the onion.
Roll dough out into evenly-sized small balls. I like to use a small scoop.
Heat your oil to 375°F and prepare to fry.
Drop dough balls into the oil. Fry the hush puppies in batches, 3 minutes on each side or until golden brown. Use your slotted spoon to turn them in the oil so they fry to golden perfection on all sides. Then, transfer to a paper towel-lined pan to drain.
Notes
Use a small cookie scoop to ensure your hush puppies are all the same size. This helps them cook evenly and avoids undercooked centers or burnt exteriors.
Use a thermometer to maintain the oil temperature at 375°F. Too hot, and the hush puppies will burn outside while remaining raw inside. Too cool, and they will absorb excess oil, becoming greasy.
Customize your hush puppies by adding extras like chopped jalapeños, shredded cheese, or chopped chives for added flavor.