I eat tahini sauce every day, it is a staple in Israeli cuisine. The most important factor is the tahini you use. It's important to note that it's not necessary the same tahini you prefer too eat raw. I always keep 2 brands, one for suace and one for eating raw and using in sweets. I also keep a whole meal tahini, which is good for eating raw or sweet, but not in lemony sauce.
Another factor is sufficient amount of water, dilution is important to realese the nuances of tahini and reduce the earthy-toasted notes to a pleasant level. Start with a ratio of one to one by volume. It should be very liquid and flow freely. If you want it thicker, refrigerate it for a few hours.
Do not add too much garlic. No more then one clove to one cup of prepared sauce. A good tahini suace doesn't have to contain garlic at all, but it does improve it.
Lemon should be added to taste, it's quite easy to get the amount right if you know what you like.
Always mix the raw tahini in it's jar very well before using, otherwise you will get too much solids or too much fat.
