Caprese Panini with Caramelized Onions

In a large skillet, heat 1 tablespoon of olive oil over medium heat. Add the sliced onions and cook, stirring occasionally, until they are caramelized and golden brown, about 15-20 minutes. Deglaze the pan with the balsamic vinegar and cook for an additional 2-3 minutes. Set the caramelized onions aside.

Preheat a panini press or grill pan over medium heat.

Lay the bread slices on a clean surface. Divide the sliced mozzarella evenly among 4 of the bread slices. Top each with sliced tomatoes and torn basil leaves.

Spread the remaining 4 bread slices with the caramelized onions. Close the sandwiches to create 4 panini.

Brush the outside of the panini with the remaining 1 tablespoon of olive oil. Place the panini in the preheated panini press or grill pan and cook for 3-4 minutes per side, or until the bread is golden brown and the cheese is melted.