In a large skillet, melt 1 tablespoon of unsalted butter over medium heat. Add thinly sliced medium onions and a pinch of salt, stirring occasionally. Cook for about 10 minutes until the onions turn golden brown and are fragrant. Drizzle in a splash of balsamic vinegar, stirring and cooking for another 2-3 minutes until well coated. Remove the caramelized onions from the skillet and set aside.

In the same skillet, add another tablespoon of butter and allow it to melt over medium heat. Assemble the Pear & Apple Grilled Cheese by layering half of the shredded sharp cheddar cheese on two slices of sourdough bread. Evenly distribute the caramelized onions, followed by thin slices of medium pear and medium apple. Top with the remaining cheese and cover with the other slices of bread.

Carefully place one assembled sandwich into the skillet. Grill for about 4-5 minutes, or until the bread is golden brown and crispy. Gently flip the sandwich to the other side using a spatula, and continue to grill for another 4-5 minutes until the cheese melts thoroughly and the crust is beautifully golden. Repeat the grilling process for the second sandwich.

Once both sandwiches are grilled to perfection, remove them from the skillet and let cool for a minute. Slice each sandwich in half with a sharp knife, exposing the gooey melted cheese and sweet fruits within. Serve warm and savor the delicious combination of flavors from the Pear & Apple Grilled Cheese with Caramelized Onions.