Cooking the Aubergine: Peel, slice, and arrange the aubergine in a well-greased baking sheet. Brush or spray the aubergine with oil on both sides.
Bake for 10-20 minutes on 200C, then flip the aubergine on the other side and bake for more 15 minutes. Take the aubergine out of the oven and mash it coarsely using a fork.
Preparing the Dressing: In a mixing bowl, mix tahini and water well using a fork until the tahini become a bit liquidy. You may need to add more water. Make sure there are no clumps.
Add vinegar, salt, pepper, cumin, minced garlic, and olive oil to the tahini mixture, mix until all combined. Add the mashed aubergine to the tahini mixture and stir well.
Notes
To cook the eggplant, you can roast it in the oven as in the instructions above or you can deep fry it, both ways are fine. Also, you can roast the eggplant over the stovetop on direct flame.
If you fry the eggplant, you may need to exclude olive oil from the ingredients.
Traditionally, the eggplant must be coarsely mashed; however, if you like it to have a silky texture, you can simply blend all the ingredients in the food processor. (Don't run the food processor too much, just a few pulses.)
You can substitute cider vinegar with lemon or lime juice if you like.
If you like it spicy, you can add ½ teaspoon of cayenne pepper to the ingredients.
Don't skip the tahini, it gives the recipe richness. If you are not a fan of its flavour, you may reduce the amount of tahini to ½ a cup.
You may need to adjust the taste; add more salt and pepper or more minced garlic if you like it garlicky.