In a large resealable bag, combine the chicken tenderloins with buttermilk, smoked paprika, cayenne pepper, garlic powder, and salt. Seal the bag, ensuring the chicken is well-coated, and refrigerate for at least 4 hours, or up to 24 hours for maximum flavor and tenderness.

While the chicken marinates, prepare the breading by mixing all-purpose flour, baking powder, salt, black pepper, garlic powder, and paprika in a large mixing bowl. Stir until evenly combined. Slowly add buttermilk from the marinade, mixing until a thick, lumpy batter forms.

Once marinated, remove chicken from the bag, shaking off excess buttermilk. Dip each tenderloin into the breading, ensuring it's well-coated. Place each coated tender on a parchment-lined tray.

In a deep skillet or heavy pot, heat about ¾ inch of vegetable oil over medium heat until it reaches 350°F. To test, drop a small amount of breading mixture into the oil; it should sizzle.

Carefully place a few coated chicken tenders in the hot oil, frying for about 5-7 minutes on each side until golden-brown and crispy. Use tongs to flip them halfway through. Transfer chicken to a plate lined with paper towels.

Enjoy your crispy buttermilk fried chicken tenders immediately while they're warm and crispy. Pair them with favorite sauces or serve with a fresh salad.