Begin by heating a large skillet over low heat and adding the butter. Once melted, add the thinly sliced yellow onions and brown sugar, stirring to combine. Let them cook gently for about 25-30 minutes, stirring occasionally, until the onions are golden, sweet, and jammy.

In a large mixing bowl, combine the ground beef, Worcestershire sauce, garlic powder, onion powder, smoked paprika, salt, and freshly ground black pepper. Mix until just combined and shape into equal-sized patties.

Once the caramelized onions have cooled, transfer them to a mixing bowl. Add mayonnaise, sour cream, minced garlic, fresh lemon juice, salt, and black pepper. Blend until smooth and creamy, then chill in the refrigerator.

Wash and chop the mixed greens or romaine lettuce for the bowl base. Dice tomatoes and cucumber, thinly slice red onion, and set aside.

Heat a skillet over medium-high heat, coat with olive oil, and add the burger patties. Cook for 8-10 minutes, flipping halfway through until nicely browned and cooked to desired doneness.

Assemble the bowls by placing a handful of mixed greens, topping with cooked beef patties, diced tomatoes, cucumbers, and red onion. Drizzle with caramelized onion aioli and finish with shredded cheddar cheese and chopped chives.