Heat the canola oil
in a large skillet over medium heat. Add the onions and cook until soft and lightly caramelized about 15 minutes. Add the mustard and a pinch of salt and cook for another 2 minutes. Remove the onions
from the pan to a small bowl and set aside.
In a medium bowl combine all the ingredients and whisk
Preheat the broiler to low.
Form the ground meat mixture into 6 equal patties. Do not over handle or compress the patties, keep them loose. This will help create a tender burger. Over mixing and compacting will result in a tough heavy burger.
Heat the canola oil a large heavy-bottomed skillet over medium-high heat.
In a small bowl combine the salt, pepper and garlic powder and season the burgers generously with the mixture. Put the patties in the skillet and cook for 4 minutes. Flip and let cook for 1 minute, then top each patty
with a piece of cheese
. Cook for another 2 minutes until the cheese is melted and the burgers are medium.
While the burgers are cooking, lightly brush the buns with melted butter
and put them on a sheet pan
until lightly toasted, about 2 minutes.
To assemble, split the buns and spread each half with about a tablespoon of the special sauce
. Put the burgers on the bottom half of each bun, top with caramelized onions, tomato and lettuce. Cover with the top half of the bun and serve.