Preheat the oven to 350°F.
In a small bowl, stir together the onion powder, paprika, chili powder and salt. Sprinkle evenly over both sides of the chicken.
1 teaspoon onion powder, 1 teaspoon paprika, 1 teaspoon chili powder, ½ teaspoon salt, 1 pound boneless
Heat the olive oil in a cast iron or other oven-safe skillet over medium-high heat. Add the chicken and cook for about 2 minutes per side, or until browned.
1 teaspoon olive oil
Transfer the skillet to the oven and bake for 18–25 minutes, or until the chicken reaches an internal temperature of 165°F in the thickest part.
Transfer the chicken to a plate and pour the juices from the skillet over it. Let rest for 10 minutes. Place the chicken and juices in the bowl of a stand mixer fitted with the paddle attachment and mix on low speed just until shredded. Alternatively, shred with two forks. Stir in the BBQ sauce.
¾ cup BBQ sauce
Increase the oven temperature to 400°F. Lightly coat a 9×13-inch baking dish with cooking spray. In a bowl, combine the smoked Gouda and mozzarella.
1 cup shredded smoked Gouda cheese, 1 cup shredded mozzarella cheese
Keeping the rolls connected, slice the entire slab horizontally into a top and bottom half. Place the bottom half in the prepared dish.
1 12-count package Hawaiian sweet rolls
Layer half of the cheese mixture over the bottom rolls, followed by the red onion, BBQ chicken, remaining cheese and pickle slices. Place the top half of the rolls over the filling.
¼ cup finely diced red onion, 12 pickle slices
In a small bowl, stir together the melted butter and ranch seasoning. Brush evenly over the tops of the rolls.
¼ cup butter, 1 teaspoon ranch seasoning mix
Cover the dish with foil and bake for 20 minutes. Remove the foil and bake for 5 more minutes, or until the cheese is melted and the tops are golden and crisp.
Cut between the rolls and serve warm.