When you are ready to make the sauce, drain and rinse the cashews. Place them in a blender along with 3/4 cup of fresh water, lemon juice and salt.
Grind into a puree, adding more water as needed, until you reach a smooth sauce.
The trick to the sauce is to use raw, unsalted cashew nuts. Raw nuts are easier to grind and turn into the most creamy tender sauce. And a high-speed blender is another key to success.