1. Peel and cut yellow onion into 4, 1/2 inch slices. 
2. Drizzle each onion slice with olive oil and season with a pinch of salt, pepper, and sugar. 
3. In a pan on medium low heat, caramelize onions for about 5-7 minutes on each side. Onions should have a nice sear on outside and soft through the middle. Set aside for assembly. 
4. Roll 3 0z balls from ground beef and then smash down into thin patties. Season with salt, pepper, and garlic powder. 
5. On medium high heat, sear burger patties in a pan or griddle with 1 tablespoon of olive oil for 2 minutes per side or until cooked through.  Add a slice of American cheese to each patty, allow the cheese to melt, and remove from the pan.
6. Assemble Flying Dutchman burger by stacking two beef patties on top of one slice of cooked onion, add a spoonful of burger sauce and top with one more onion slice. 

Burger sauce: 

1. Combine all ingredients for burger sauce together in a bowl and whisk together to combine. Spoon sauce on top of the burgers or to the side for dipping.