Set up grill for direct cooking over medium heat. Oil grate when ready to start cooking.
Lay out 4 tortillas; spread each with half of the herb cheese. Divide and top each tortilla with salmon, capers, and jack cheese. Top with remaining tortillas.
In a small bowl, combine sour cream with dill; set aside. Grill tortillas on hot oiled grill 3 to 4 minutes per side or until cheese has melted. Serve hot topped with sliced avocado, cherry tomatoes, and onion rings. Garnish with creme fraiche.