Heat a skillet over medium-high heat and add in the olive oil and butter. Toss in the diced onion and cook, stirring occasionally, for about 30 minutes, until the onions turn a deep, golden brown color. Remove from heat and set aside.
In a separate mixing bowl, combine the ground beef, mayo, 1 tsp seasoned salt, garlic powder, black pepper and caramelized onions. Use clean hands to combine the meat mixture and shape into 4 hamburger patties.
Season each side of the patties with the remaining seasoning salt and grill over medium-high heat, until cooked to desired temperature (about 3 to 5 minutes per side).
Just before removing from the grill, top with the provolone cheese and let melt slightly. Enjoy with your favorite burger toppings.
Nutritional facts are calculated for just burger and cheese, no buns or toppings.