1 lemon, sliced 1/4 inch thick, plus 1 tablespoon juice
1 1/2 teaspoons minced fresh dill, stems reserved
2 (6‐ to 8‐ounce) skin‐on salmon fillets, about 1 1/2 inches thick
Salt and pepper
1/4 cup sour cream
1 teaspoon Dijon mustard
1. Fold sheet of aluminum foil into 12 by 9-inch sling and press widthwise into slow cooker. Arrange lemon slices in tight single layer in bottom of prepared slow cooker. Scatter dill stems over lemon slices. Pour water into slow cooker until it is even with lemon slices (about 1/2 cup water). Season fillets with salt and pepper and place skin side down on top of lemon slices. Cover and cook until salmon is opaque throughout when checked with tip of paring knife and registers 135 degrees, 1 to 2 hours on low.
2. Combine sour cream, mustard, lemon juice, and minced dill in bowl and season with salt and pepper to taste. Using sling, transfer fillets to baking sheet. Gently lift and tilt fillets with spatula to remove dill stems and lemon slices and transfer fillets to individual plates; discard dill stems, lemon slices, and poaching liquid. Serve with sauce.