1. Heat a large iron skillet over medium-high heat. Set a timer for 9 minutes. Add the onion quarters and cook, flipping after 4 minutes. With 6 minutes left on the timer, add the tomatillos and chilies. Flip both after 3 minutes. Add the garlic with 4 minutes left. When all are slightly blackened transfer to a food processor. Toss in the cilantro and sugar, and process until very smooth.

2. Clean out the iron skillet, then pour in the oil over medium-high heat. Carefully pour in the tomatillo mixture. Cook for 2 minutes or until it has thickened. Pour in the chicken broth and lime juice. Bring mixture to a boil, then reduce to a simmer. Cook for 10 minutes. Season with salt to taste.

3. Time to stack. Place a tortilla on a plate. Top with a little bit of sauce and sprinkling of cheese. Repeat process two more times. Place plate in a microwave and cook until cheese has melted, about a minute.