In a large skillet, heat olive oil and sliced onions. Cook onions 25-30 minutes or until onions are soft and caramelized. Add fig preserves and cook additional 2-3 minutes.
In a large bowl, add ground beef, salt, pepper, garlic powder and Worcestershire sauce. Mix until evenly combined.
Divide the meat into 8 equal portions. Using your fingertips, press the portions of meat into 1/4-inch patties.
In a small bowl, combine blue cheese and 1 tablespoon of the fig onion mixture. Divide mixture into 4 equal portions. Place a portion of the blue cheese mixture onto half of the patties, save the rest for topping. Add one of the remaining patties to the top of the patties with blue cheese, and pinch to seal.
Place the burgers on a prepared grill and cook for 7 minutes each side. Remove patties and let rest for 5 minutes. Place lettuce and tomato on bottom of each bun. Add patty and top with remaining fig onion jam.