Place the salmon fillets on a work surface, skin side down. Sprinkle evenly with sugar, salt, and pepper. Place the dill on top of one half and then, like a book, fold the two halves together. Carefully and tightly wrap plastic wrap around the fillets and place it in a baking dish. Place a slightly smaller dish on top weighted down (I like to use a sack of flour). Refrigerate for 2 - 4 days, flipping the wrapped fillets each day.
Remove weights and discard the wrap. Gently rinse the salmon under cold water, removing the all of the salt, pepper, sugar, and dill.
Slice the salmon at 45 degree angle, as thinly as possible. Serve with a dill mustard sauce and pumpernickel bread.