Assemble quesadillas: Place 4 tortillas on a work surface. Dividing evenly, scatter chorizo, bell pepper, and scallions over each, leaving a 1/2-inch border all around. Sprinkle 1/2 cup cheese over each, and top with remaining tortillas. Press lightly to seal.
Place 1 quesadilla on a paper towel. Top with another paper towel, a quesadilla, and a third paper towel. Microwave the 2 stacked quesadillas on high for 2 minutes or until cheese has melted.
Carefully unstack quesadillas (they will be very hot), and remove paper towels. Place on a platter. Repeat with remaining 2 quesadillas.
Cut each quesadilla into 4 wedges and serve with salsa, if desired.