Whiskey Bacon Jam Smash Burger

Ingredients

• 2 yellow onions, thinly sliced
• 6-8 slices thick-cut bacon, chopped
• 2 tbsp balsamic vinegar
• 1 tsp smoked paprika
• 1 tsp coarse black pepper
• 2 tbsp bourbon or whiskey of choice
• 1 lb 80/20 ground beef, divided into 5 equal portions
• 5 slices American cheese
• 5 slices pepper jack cheese
• Romaine lettuce leaves
• 1 tomato, sliced
• Dijon mustard
• 5 pretzel hamburger buns