I used Zucchini,but you can use lauki/Ghiya. I used lemon juice in the end, but you can replace with tamarind/pulp/paste. Its not easily available where I live. Tamarind will make the sambar a bit dark in color. Since Arhar/Toor dal can cause gas, I use Ginger in the end as it makes it easily digestible and gives a very nice flavor.