Preheat the oven to 400°F and line a large rimmed baking pan with parchment paper and set aside.
Grate 8 ounces parmesan cheese and spread in a thin layer over the parchment paper.
Slice the 3 yellow onions very thin, about ⅙ inch wide (slicing with a mandolin will give the best results), and lay them over the top of the parmesan cheese in a single layer.
Brush the onions with 2 tablespoons avocado oil to coat.
Sprinkle 2 teaspoons paprika, 1 teaspoon coarse sea salt, 1 teaspoon garlic powder, ½ teaspoon seasoning salt, and ¼ teaspoon ground black pepper over the tops of the onions.
Bake for 25 to 30 minutes until they are golden brown and crispy. Let cool on the pan for 10 minutes before breaking up and enjoying.