Combine the dill, sugar, vodka, salt and lime zest in a small bowl and stir until well mixed.
Spread the mixture over the salmon flesh. Cut the side of salmon in half crosswise. Fold each piece in half so the flesh is touching and the marinade is on the interior. Wrap the pieces tightly in plastic wrap and refrigerate for 2 days.
Slice the salmon thinly on a bias and serve.
The gravlax is delicious served on its own, or try it on a bagel with cream cheese, sliced tomatoes, capers and sliced red onions.