In a heavy skillet, heat the oil over medium high heat. Season the salmon filet with the fajita seasoning and add it to the pan. Cook until well browned on both sides, and remove from pan.
Add the bell peppers and onions and cook until softened. Add the salsa, beans, and corn. Add the salmon back to the pan, and break up with a spatula. Continue cooking until salmon is cooked through and add the lime juice.
In a separate skillet, melt the butter. Add one tortilla, sprinkle a bit of cheese and some of the salmon mixture. Fold the tortilla in half and continue cooking until cheese is melted, and both sides are browned. Continue with the remaining tortillas.
Serve topped with sour cream, cilantro, and hot sauce if desired.