Sarah's Stewed Taco Burgers
After I moved to Oklahoma, I quickly discovered most every burger joint has their version of an onion burger. My version takes the Oklahoma onion burger south of the border. Top with lettuce, cheese, avocado slices, black olives, and Mexican crema.
You can add as much or little sliced onion to the tomato sauce as you wish. I normally aim for between 1/4 and 1/2 cup sliced onion.