Add 3 to 4 tablespoons of olive oil to a large non-stick skillet, along with the sliced onions. Heat over medium-high and saute, stirring occasionally, until onions begin to sweat and begin turning translucent, about 5 minutes.
Reduce the heat to medium and continue sauteeing, stirring occasionally, until onions begin to brown, about 15 minutes.
Add the sliced jalapenos, and reduce the heat to medium-low. Continue cooking, stirring occasionally, until onions are deeply browned and caramelized, about 25 to 30 minutes. Note: If onions begin to stick to the pan at any point, you can de-glaze with a few tablespoons of water (or beer or wine).
Make the Burgers:
While the onions are caramelizing, add all of the ingredients for the burger meat to a mixing bowl and use your hands to mix everything well (this will take a couple minutes of meat kneading). Cover with plastic wrap and refrigerate until ready to grill.
Preheat grill to medium-high and form 3 or 4 burger patties out of the meat.
Place patties on the hot grill and cover. Cook until grill marks appear, about 3 minutes. Flip burgers and cook to desired done-ness, about another 3 minutes.
Turn off the heat of the grill and add cheese slices to the burger patties. Cover the grill and let burgers sit until cheese has melted, about 1 minute.
Remove burgers from grill.
Toast burger buns, then form an excellent burger by topping a grilled burger patty with desired amount of caramelized onions and jalapenos.
Enjoy!
Notes
*You can also use ground beef or ground turkey. If using ground turkey, add 1 to 2 tablespoons olive oil to get the meat to bind together better.