If the dressing has been refrigerated for several days, it tends to lose its acidity, so you may want to add a few extra droplets of lemon juice to perk it up.
1/2cupeach: tahini and water
A generous 2 tablespoons of lemon juice
Whisk tahini and water to blend. Whisk in 2 tablespoons of lemon juice and a sprinkling of salt. Taste and adjust seasonings, including a few extra drops of lemon juice and salt. (Can be covered and refrigerated several days.)