In a skillet over medium heat, melt a tablespoon of butter. Add the sliced onions, seasoning with a pinch of salt, and sauté until golden and sweet-smelling, about 10-15 minutes.

While the onions are cooking, season the ground beef with salt and pepper. Form it into two patties, roughly the size of your bread slices.

In the same skillet, push the caramelized onions to the side and add the beef patties. Cook for about 3–4 minutes on each side for a medium finish. Add cheese on top right before flipping.

Spread a thin layer of butter on one side of each slice of bread. On the non-buttered side, layer your patty, sautéed onions, and cheese. Top with another slice of bread, buttered side facing out.

Wipe the skillet down and heat it back to medium-low. Carefully place the sandwiches in the skillet and cook until the bread is golden brown and crispy, about 3–4 minutes per side.

Once crispy and golden, slice the sandwiches in half and serve with pickles or a simple salad.