Preheat the oven to 350 degrees F (175 degrees C).

Make the salmon: Place salmon fillets into a shallow baking dish. Whisk melted butter, lemon juice, and Cajun seasoning together in a small bowl; drizzle over salmon.

Bake salmon in the preheated oven until until fish flakes easily with a fork, about 20 minutes.

While the salmon is baking, make the salsa: Mix corn, black beans, tomato, red onion, and cilantro in a bowl.

Flake cooked salmon into smaller pieces with a fork.

Divide flaked salmon, salsa, and Cheddar cheese among warm tortillas. Wrap tortillas around filling and serve with sour cream and guacamole.