Preheat a panini press or skillet over medium heat.
Spread butter on one side of each bread slice.
Spread pizza sauce on the unbuttered side of half the bread slices.
Top with mozzarella cheese, pepperoni, olives (if using), and Italian seasoning.
Place the remaining bread slices on top, buttered side out.
Grill in the panini press or skillet until bread is golden and cheese is melted, about 3-4 minutes per side.
Serve hot and enjoy.