In a large skillet over medium heat add the oil and butter. When the butter begins to melt add in the onions slices. Gently stir the onions around to coat. After 5 minutes, sprinkle with the salt and continue to cook until the onions turn soft and start to take on a golden brown color.. Turn the heat off and set aside. Do not burn them. If they start to burn, turn the heat down. Stir frequently. ~20-30 minutes.
Preheat the oven to 350F. Line a large rimmed baking sheet with parchment paper.
Spread half of the chips in a single layer over the baking sheet.
Top with half of the pulled pork, half of the cooked onions, 1 1/2 cups of cheddar and 1 1/2 cups of Monterey Jack cheese.
Drizzle 1/4 cup of the Coke BBQ sauce over top.
Create another layer of chips, top with the remaining pulled pork, onions, bbq sauce then cheese. Bake for 8-15 minutes or until the cheese is melted and the chips are golden brown.