Preheat the oven to 390°F (200°C) or preheat your air fryer to 390°F.
Slice the chicken breast into 1/2-inch thick pieces, then cut each piece into 2–3 nugget-sized pieces.
Place the melted unsalted butter in a shallow bowl for dipping.
In another bowl, whisk together the rice flour, garlic powder, ground paprika, salt, and black pepper until evenly combined.
Dip each chicken nugget first into the melted butter, then coat thoroughly in the rice flour mixture, shaking off any excess. Place coated nuggets on a parchment-lined baking sheet or directly into the air fryer basket in a single layer.
If baking, bake the nuggets on the prepared sheet for 15–18 minutes or until golden brown and cooked through (internal temperature 165°F). If using an air fryer, air-fry for 7–8 minutes or until golden and cooked through; cook times may vary by appliance.
Remove the nuggets when done and let rest a minute before serving.