Soak raw cashews in enough water to fully cover them overnight. Drain and rinse when ready to use.
Place cashews, cold water, lemon juice and sea salt in carafe of high speed blender. Blend on high until smooth.
Add harissa paste 1 teaspoon at a time until desired level of heat is reached. I like to add a full Tablespoon but some find that too spicy.
Once desired level of heat is achieved, you can add water 1 teaspoon at a time to reach the thickness you like best.