Begin by gathering all your ingredients. Chop the roasted red peppers, slice the Kalamata olives and pepperoncini, and thinly slice the red onion. Crumble the feta cheese and set it aside.
Take a slice of sourdough bread and spread a generous layer of softened butter on one side. On the unbuttered side, layer the mozzarella cheese, followed by the roasted red peppers, Kalamata olives, pepperoncini, red onion, and crumbled feta. Top it off with another slice of mozzarella cheese before placing a second slice of sourdough on top, buttered side out.
Place your skillet or griddle over medium heat. Allow it to warm up for a couple of minutes.
Once the skillet is hot, carefully place your assembled sandwich in the pan. Cook for about 3-4 minutes or until the bottom is golden brown and crispy.
Using your spatula, gently flip the sandwich over. Cook for an additional 3-4 minutes, ensuring the cheese melts beautifully and the bread achieves that perfect golden crust.
Once both sides are golden and the cheese is melted, remove the sandwich from the skillet. Let it cool for a minute before slicing it in half. Serve it with your favorite dipping sauce.
