You can buy Tahini but doing it yourself is quite simple and more cost effective.
Tahini is a necessary part of Hummus but can also be used to mix into salad, drizzled over vegetables (I find a mixture of olive oil and tahini poured over cauliflower especially nice) so it has multiple uses. Make as much as you want but remember it’s only good for a week or so in the fridge.
For Tahini all you need is raw sesame seeds and some mild flavor oil (such as canola oil).
Brown the sesame seeds lightly in a pan over medium heat. Stir frequently. When they just begin to smoke and you smell the aroma pull them off the heat (they will go from light brown to dark/burned in seconds so don’t take your eyes off them) and put them into a mixing bowl and stir to cool them quickly as they will continue to cook until they cool down.
When cooled add the seeds to a food processor and add a tiny pinch of salt (not necessary but I think it brings out the flavor) and just a drizzle of oil (a couple teaspoons). Puree in the food processor a while then scrape down the sides with a spatula. The mix will be very chunky at first, so add a tiny bit more oil and puree some more. Continue this process until you get a thick liquid.
You’re aiming for something about the consistency of maple syrup.
Store in the refrigerator for up to a week. As I mentioned this is usually the base for hummus but is also nice drizzled over warm vegetables or as a dip.