Preheat oven to 350°F. Heat oil in medium cast-iron skillet on medium high heat. Add onion and garlic, cook and stir until deep golden brown and slightly charred, about 5 minutes. Remove from skillet; mix with 3 teaspoons of the Aji Amarillo Seasoning.
Place 1 ½ cups Oaxaca cheese and ½ cup Cotija cheese in skillet. Layer with the onion mixture and cooked chorizo, top with remaining cheese.
Bake until the cheese is bubbling, about 5 to 7 minutes.
Remove from oven and garnish with cilantro, sliced green onions and 1 teaspoon Aji Amarillo seasoning. Serve hot with tortilla chips.
