Soak the cashews in boiling water for 20 minutes and set aside.
Heat the olive oil in a large skillet over medium heat. Add the diced onions and stir them around to coat in the oil. Then spread them out and let them cook untouched for about 6-8 minutes. Season with a pinch of salt.
As the onions continue to cook, they'll start to stick to the pan a bit. Deglaze the pan with a splash of water, broth, or any kind of vinegar then give it a good stir to break up the fond (the flavorful bits stuck on the bottom). If you notice the onions starting to brown too quickly, turn the heat down a little.
Repeat this process deglazing and stirring as you notice the onions sticking. You'll only need to deglaze a couple of times. Cook until the onions have deepened in color and are fragrant, about 25-30 minutes. Remove the skillet from the heat.
Drain and rinse the cashews then add them to the base of a high-powered blender with fresh water, coconut aminos, kosher salt, onion powder, garlic powder, and a couple cracks of freshly ground black pepper. Blend on high until completely smooth. Add the vinegar of choice or lemon juice and blend again.
Transfer the cashew cream mixture to a medium bowl and fold in the caramelized onions. Season to taste with more salt or acid as needed. Let chill covered in the fridge for about an hour before serving to allow the flavors to develop. Serve with potato chips or fresh veggies.