In a large mixing bowl, combine the fine cornmeal, all-purpose flour, kosher salt, baking powder, baking soda, Cajun or Creole seasoning, garlic powder, and granulated sugar. Whisk these dry ingredients together until they are well mixed.
Grate the small yellow onion (about 1/4 cup) and add it to the dry mixture. The onion adds a lovely flavor that complements the cornmeal perfectly.
In another bowl, whisk together the large egg and buttermilk until smooth. The buttermilk adds moisture and tanginess to the hush puppies.
Pour the wet mixture into the bowl with the dry ingredients. Stir gently until just combined. Be careful not to overmix; a few lumps are okay!
In a deep fryer or heavy-bottomed pot, heat the canola or vegetable oil over medium-high heat until it reaches 350°F (175°C). You can test the temperature by dropping a small bit of batter into the oil; it should sizzle and rise to the surface.
Using a spoon or a small scoop, carefully drop balls of the batter into the hot oil, making sure not to overcrowd the pot. Fry them in batches for about 3-4 minutes, or until they are golden brown.
Once cooked, use a slotted spoon to remove the hush puppies from the oil and place them on paper towels to drain excess oil. Serve them warm with your favorite dipping sauce or alongside a main dish like Southern Fried Chicken.