Heat at least 3” of oil in a Dutch oven or deep cast iron skillet until it reaches 350°F. You want the oil deep enough to cover as much of the chicken as possible. Submerging the chicken all the way in the oil will produce the most even cooking.
Prepare a dredging station to batter the chicken while the oil is heating. In one bowl, pour the buttermilk. In a second bowl, mix together smoked paprika, black pepper, sea salt, onion powder, and flour. Whisk until combined evenly.
Batter the chicken pieces by dipping them first into the flour mixture, then into the buttermilk mixture, and one more time into the flour mixture. Set the battered chicken on a separate plate.
When the oil has reached 350°F, place several pieces of battered chicken into the oil. Cook for approximately 12 minutes, turning once halfway through cooking if the chicken is not fully submerged in the oil. Cook until the chicken is deep golden brown and the internal temperature reaches 165°F. Lift the chicken from the oil with a slotted spoon and place on a paper bag or paper towels to soak up the excess oil. Continue cooking the chicken in batches.