How to Make It
In a large, preferably oval, slow cooker, place a piece of foil long enough to overhang sides. Coat foil and slow cooker sides with cooking spray.
Chop enough dill fronds to equal 2 tablespoons; set aside. Line slow cooker bottom with remaining dill, orange slices, and lemon slices. Sprinkle with 3 tablespoons water.
Season flesh side of salmon with salt and pepper; place fillet, skin side down, on top of citrus. Cover and cook on LOW 2 1/2 hours or until fish flakes easily when tested with a fork or until desired degree of doneness. Using foil as handles, lift salmon fillet out of slow cooker; let stand 10 minutes. Lift fillet off herbs, and transfer to a serving platter.
While salmon cooks, combine reserved dill fronds, sour cream, mayonnaise, lemon rind, lemon juice, and mustard in a bowl; refrigerate. Serve salmon warm or at room temperature with dill cream sauce and orange and lemon wedges, if desired.