Mix turkey with cumin and garlic powder; set aside.
Combine cheeses in another bowl.
Lay out 4 tortillas; add quarter of cheese mixture to each, then turkey and optional peppers and onion.
Top each with another tortilla; gently press to seal.
Melt pat of butter in large skillet over medium; add one quesadilla.
Cook 2-3 minutes until bottom golden; carefully flip and cook 2-3 minutes more until cheese melted and other side golden.
Remove; repeat with remaining quesadillas, adding butter as needed.
Cut each into 4 wedges; serve immediately with sour cream and salsa.