If your babaganoush comes out bitter, your eggplant may be old or not in season. I recommend selecting only fresh eggplants, which tend to have milder, sweeter flesh. Furthermore, it’s possible that the tahini paste you used has a naturally bitter profile or that you added too much during the mixing process. Always be sure to taste your babaganoush as you go so that you can adjust the seasoning to counteract any unwanted bitterness. You may also try adding extra fats, such as olive oil or Greek yogurt, to balance out any bitterness you taste.