Heat 2 tablespoons of olive oil in a skillet over medium heat. Add 2 sliced medium onions, season with salt and pepper, and cook for about 15 minutes until golden brown.

In the same skillet, push onions to the side and add 6 strips of bacon. Cook for 5-7 minutes until crisp, then drain on paper towels.

Assemble sandwiches with 2 slices of cheese, crispy bacon, and caramelized onions sandwiched between 2 slices of bread.

Butter the outer sides of each sandwich generously to help with browning.

Cook in a preheated skillet for 4-5 minutes per side until golden and cheese is melted.

Allow to cool slightly, then slice in half to reveal the gooey interior.

Serve warm with tomato soup or salad.