Step 1: Prepare the Caramelized Onions

1. Heat olive oil in a large skillet over medium heat. Add the sliced onions and a pinch of salt.
2. Cook, stirring occasionally, for 20 minutes, or until the onions are soft, golden, and caramelized. If desired, sprinkle sugar over the onions during the last 5 minutes for added sweetness. Remove from heat and set aside.

Step 2: Cook the Beef Patties

1. In a large bowl, combine the ground beef, salt, pepper, garlic powder, and onion powder. Mix gently to avoid overworking the meat.
2. Divide the mixture into 4 equal portions and shape them into thin, oblong patties slightly larger than the bread slices (they will shrink during cooking).
3. Heat a skillet or griddle over medium-high heat. Cook the patties for 3-4 minutes per side, or until fully cooked and browned. Set aside.

Step 3: Assemble the Patty Melt

1. Butter one side of each slice of bread. Place 4 slices, butter-side down, on a clean surface.
2. Layer each slice with a piece of cheese, a cooked patty, caramelized onions, and another slice of cheese. Top with another slice of bread, butter-side up.

Step 4: Grill the Sandwiches

1. Heat a skillet or griddle over medium heat. Place the assembled sandwiches in the pan, working in batches if necessary.
2. Cook for 3-4 minutes per side, or until the bread is golden brown and the cheese is melted. Press gently with a spatula to help the sandwich hold together.

Step 5: Serve

1. Slice the sandwiches in half and serve immediately. Pair with fries, salad, or soup for a complete meal.