Soak the chicken tenders in the buttermilk and salt for 1 to 4 hours in the refrigerator.
Combine the flour, cornstarch, onion powder and black pepper in a shallow pan.
Lift the tenders from the buttermilk, press them firmly into the flour mixture and rest them on a rack for 10 minutes.
Heat 1 inch peanut oil in a heavy pot to 350°F.
Fry the tenders in three batches for 3 to 4 minutes per side until pale gold, crisp and 165°F at the center.
Brown the butter in a small saucepan for 3 to 4 minutes until it smells nutty, then remove it from the heat and stir in the honey and pepper flakes.
Drizzle the warm honey butter over the drained tenders and turn them once to coat lightly, then serve within 10 minutes.