Julienne cut the onion into fine strips, then place them in a hot pan with some olive oil.
Add some butter to the pan and continuously move the onion strips to avoid burning.
While still moving the onion strips, slowly add the sugar then season to taste with salt and pepper. Cook until each strip reaches a light brown color. Allow cooling before serving.
Place the foil on a flat surface, then cut out 4 squares approximately 8 inches in size; grease each square with cooking spray. Make sure the foil squares are large enough so that no food can escape.
Cut the FUD Muenster Cheese into 1-inch thick slices, then place each slice on a sheet of foil. Stack the following ingredients on top of the Muenster cheese slices in this order: shredded FUD Oaxaca cheese, diced steak, caramelized onions, green salsa and cilantro.
Close the foil tightly, folding each of the four sides inwards then place it on the grill for about 7 minutes.
On a grill, place the tomatoes, chilies, garlic and tomatillos; grill until lightly charred. Remove the seeds from the peppers, then blend with salt. Place the mixture in a bowl and let cool. Once cold, add the chopped cilantro on top.