Fruit is the fix and it works better than sugar. Mango, pineapple, peach, or roasted carrot or roasted red pepper if you want it savoury. It rounds bitterness off rather than covering it.
Add a little, blend, taste, repeat, and stop before you have made chutney. A splash of vinegar or lime afterwards lifts the whole thing and helps it keep, and a small pinch of salt suppresses bitterness more than people expect.