I think i went a bit overkill on the cayenne by mistake and don't know what to add - besides lots of cilantro, which I already did.
You can try removing the chicken and then whisking in some heavy cream. Start with a half cup. Sour cream would probably work too. If it's still hot whisk in more cream. It will change the appearance of your sauce but the flavors should still come through. When you are satisfied add the chicken back in.
Yoghurt would work too, as a stir-in, and like the sour cream, is in the same taste arena as the preserved lemon.
Another (delicious!) stir in is ghee. I would want ghee in everything anyway, but it works especially well as a spice-tamer.
You could also increase the volume of the liquid portion and add in some more of all the other spices to balance. You'll have more delicious sauce at the end of it, with which you can do fun stuff like marinate tofu or even spoon it over rice and eat straight up.