Lay out 4 tortillas; spread the herb soft cheese among them. Divide and top each tortilla with salmon, capers, and cheese. Top with remaining tortillas.
In a frying pan large enough for the tortillas, heat 1 to 2 tablespoons of vegetable oil over medium heat. Cook tortillas in the frying pan for 2 to 3 minutes on each side or until cheese has melted and the tortillas are golden brown; turn them with a large spatula.
In a small bowl, combine sour cream with dill; set aside.
Serve the tortillas hot - topped with sliced avocado, cherry tomatoes, and onion rings. Garnish with a dollop of crème fraîche if desired, and serve with the sour cream & dill mix.