Add mayonnaise, sour cream, dill, lemon juice, lemon zest, salt, and pepper to a bowl. Stir until smooth and very well combined.
Add cream or milk if you like a looser texture.
Cover and refrigerate for 10 minutes if you have time. Taste and adjust salt as needed. Serve chilled or at cool room temperature.
Notes
If needed, you can use 2 tsp dried dill (plus more to taste) in place of the fresh dill, but fresh dill is really the star of the recipe.The batch makes about 1 cup of dill sauce for salmon.