Whisk 1 cup buttermilk, 1 tablespoon of the lemon pepper seasoning, 1 teaspoon finely grated lemon zest, 1 tablespoon lemon juice, 1 teaspoon garlic powder, and 1 teaspoon of the smoked paprika together in a large bowl.

Pat 2 pounds boneless, skinless chicken breasts dry with paper towels. Cut lengthwise into 1-inch-wide strips. Trim any thinner ends so that they’re all roughly the same size. Add to the marinade and toss until coated. Cover and marinate for 30 minutes at room temperature, or refrigerate for up to 2 hours.

Heat the oven to 425°F or an air fryer to 400ºF. If using the oven, line a rimmed baking sheet with aluminum foil or parchment paper and coat lightly with cooking spray.

Stir 2 cups panko breadcrumbs, ½ cup grated Parmesan cheese, the remaining 1 ¼ teaspoons lemon pepper seasoning, ½ teaspoon dried thyme, and the remaining ½ teaspoon smoked paprika together in a pie plate or large rimmed plate.

Working with 1 chicken tender at a time, remove from the marinade and let the excess drip off. Place in the breadcrumb mixture and turn to coat, pressing gently so that the tenders are evenly coated. Place on the baking sheet, spacing them evenly apart.

If using the oven, bake for 20 minutes. Flip each chicken tender and bake until cooked through, golden-brown, and crisp, 10 to 15 minutes more. If air frying, arrange the chicken in a single layer in the air fryer basket (cook in batches if needed). Air fry, flipping halfway through, until cooked through, golden-brown, and crispy, 10 to 12 minutes total. Make the sauce a few minutes before the chicken is ready.

Heat 1 stick chopped unsalted butter, 2 minced garlic cloves, 1 ½ teaspoons lemon pepper seasoning, and ¼ teaspoon red pepper flakes if using in a small saucepan over medium heat until the butter is melted and the garlic is fragrant. Transfer to a serving bowl.

Serve the chicken tenders with the garlic butter sauce on the side, or lightly brush each chicken tender with the sauce just before serving.