Heat a large skillet over medium-high heat. Add onion and saute until golden brown. Remove onions from skillet.
Turn heat down to medium.
Begin assembling quesadillas. Cover one side of tortilla with bbq sauce. On one half of tortilla, layer cheese, pulled pork, onion, and another later of cheese. Fold in half.
Repeat assembly for all four quesadillas.
Using same skillet, add oil of choice. Add two quesadillas and allow bottom side to toast until golden brown, or desired doneness. Flip quesadillas to heat other side. Remove from skillet.
Repeat with other assembled quesadillas.
Slice each quesadilla into triangles, serve with side of sour cream and barbeque sauce.