I start by whisking the buttermilk, lemon pepper seasoning, lemon zest, lemon juice, garlic powder, and a bit of the smoked paprika together in a large bowl. Then I pat my chicken breasts dry and slice them into even strips so nothing cooks unevenly. I toss the chicken right into that marinade, cover it, and let it sit for at least 30 minutes on the counter, or up to two hours in the fridge if I'm prepping ahead.
While the chicken marinates, I heat my oven to 425°F, or my air fryer to 400°F if I'm using that instead. I line a baking sheet with foil and give it a light coat of cooking spray so nothing sticks. In a shallow dish, I mix the panko, Parmesan, remaining lemon pepper seasoning, thyme, and the rest of the smoked paprika until it's evenly combined.
This is the messiest but most satisfying part for me. I pull each chicken strip from the marinade, let the excess drip off, then press it firmly into the panko mixture on all sides. I really push down so the coating clings well, then set each piece on my prepared baking sheet with a little space between them.
If I'm baking, I pop the tray in for about 20 minutes, flip each tender, then bake another 10 to 15 minutes until they're deeply golden and cooked through. In the air fryer, I arrange them in a single layer, cooking in batches if needed, and air fry for 10 to 12 minutes total, flipping halfway. Either way, I always check that the internal temperature hits 165°F.
While the chicken finishes cooking, I melt the butter in a small saucepan with minced garlic, lemon pepper seasoning, and red pepper flakes if I'm in the mood for heat. I let it simmer gently just until fragrant, then pour it into a small serving bowl. I either serve it on the side for dipping or brush it directly over the hot tenders right before serving.