Marinate the chicken: In a large bowl, whisk the buttermilk with a pinch of salt. Add the chicken tenders, cover, and refrigerate for 30 minutes to 2 hours. This keeps them juicy and helps the coating cling.
Prepare the spicy dredge: In a shallow dish, combine flour, cornstarch, paprika, garlic powder, onion powder, salt, black pepper, and cayenne (adjust heat to your preference). Stir to distribute spices evenly.
Dredge the tenders: Remove chicken from the buttermilk and let excess drip off. Dredge each piece in the seasoned flour, pressing gently so the coating adheres well. Place on a rack while you heat the oil.
Heat the oil: In a heavy skillet or Dutch oven, heat about 1 inch of oil to 350°F (175°C). Use a thermometer to keep track; maintaining steady heat is key for a crisp crust.
Fry the chicken: Working in batches, fry the tenders 3–4 minutes per side, until golden brown and crisp and an internal thermometer reads 165°F (74°C). Transfer to a rack or paper-towel-lined plate to drain.
Make the Nashville hot glaze: In a small saucepan, melt the butter over low heat. Stir in hot sauce, brown sugar, and apple cider vinegar until smooth and glossy. Keep warm.
Toss with heat: While the tenders are hot, brush or toss them with the hot glaze until well coated. For a more intense heat, drizzle more glaze and toss again.
Serve immediately: The crisp crust and juicy interior are best enjoyed hot. Serve with pickles, a cool side of coleslaw, or creamy dipping sauce.