Caramelize the onions.

Cup of Yum
1. Caramelize the yellow onions. I followed Bon Appetit’s instructions on caramelizing onions. But here’s an abridged version of what I did. Thinly slice your onion.Add two tablespoons of butter or bacon grease to a pan over medium heat. Once melted and sizzling, add the onions.Stir well for 30 seconds or so, until the onions are coated in butter/bacon grease.Reduce heat to medium-low and cook for 15-20 minutes, stirring frequently. I stopped here (step 6 of Bon Appetit’s instructions) because I was hungry. Even at this stage, the onions will take on a lovely sweet, roasted quality. For truly caramelized onions, you’ll want to keep cooking for an additional 15-20 minutes or beyond, depending on how dark you want your onions. Go ahead and cook them to your desired doneness for this recipe.

Assemble and cook the chorizo quesadillas.

1. Bring a large skillet or griddle to medium heat. Assemble a quesadilla on a cutting board. Divide the three cups of shredded pepper jack cheese into four even portions. 
2. Sprinkle one pile of shredded cheese over half of one tortilla. Add half of the cooked chorizo, followed by half of the caramelized onions, distributing them each evenly. Top with another of the piles of shredded cheese. 
3. Fold the naked half of the tortilla over the top of the side with fillings. Repeat step above with the second quesadilla.
4. Place quesadillas into a large pan or put on a griddle (you may need to cook one at a time, depending on your cooking surface).
5. Cook for 5-7 minutes on each side, or until crisp and toasty looking. 
6. Remove from heat and cut into four slices. Serve with your favorite salsa.