Mix salsa and cream cheese together and set aside until serving.
Heat griddle on medium heat while preparing the quesadillas.
On half of a tortilla sprinkle cheese, onion, and dot with teaspoons of chili. Sprinkle with fritos. Close and spread top with butter.
Place on hot griddle buttered side down and butter other side. Cook until golden brown and flip. Continue to cook until other side is golden brown and cheese has melted. Continue with the process until all quesadillas have been made.