Pat hot dogs completely dry with paper towels, then skewer with long wooden skewers. In a large bowl, whisk together flour, cornmeal, sugar, baking powder, salt, baking soda, black pepper, and cayenne.
In a small bowl, combine buttermilk and eggs, then pour into dry ingredients and mix until just combined. Pour batter into a tall glass and let sit while oil heats.
In a large pot over medium heat, add enough oil to come halfway up the sides and heat to 375°. Dip hot dogs into batter and coat evenly. Fry hot dogs, 4 to 5 at a time, until golden, 5 minutes, turning as necessary. Use tongs to remove from oil and place on a paper towel–lined plate. Fry remaining hot dogs, letting oil come back to temperature between batches.
Serve with ketchup and mustard.