Take salmon out of the fridge so it can come to room temperate. It will cook more evenly. Preheat oven to 350 degrees F. Line a baking sheet with parchment paper and set aside.
In a medium, wide bowl, mix together: bread crumbs, parmesan, 2 tbsp dill, parsley, 2 tbsp lemon juice, melted butter, salt, and pepper.
Spread a thin layer of mustard on salmon fillets. Dip and press each fillet (individually) in the bread crumb mixture, mustard side down. Arrange on lined baking sheet. Place into the oven and bake for 18 minutes. Baking time will depend on thickness of salmon fillets. If salmon fillets are less then 1-inch thick, bake for 14-15 minutes.
While the salmon is cooking, mix together: mayonnaise, sour cream, garlic powder, remaining dill, and remaining lemon juice in a small bowl. Season with salt and pepper to taste. Serve with salmon.