Make Ahead: Mix the paprika, coriander, cumin, and kosher salt.  Coat the chicken thighs in the spice mix, cover and refrigerate for at least 4 hours (preferably overnight).  

Take the chicken out of the refrigerator.  Heat the olive oil in a sauteé pan over medium heat.  Place the chicken in the pan, skin-side down, and cook undisturbed until well-browned, approximately 10 minutes.

Remove the chicken from the pan and add the garlic and onion.  Cook for 5-10 minutes or until softened.  Add the tomato paste and cook for an additional 3 minutes.  Add 1 cup of water to the pan and using a rubber spatula or wooden spoon, scrape the bottom of the pan to release all of the good browned bits.  Add the kumquats plus ½ of the parsley and dill.  Place chicken, skin side up, back in the pan.  Cover and simmer for another 10 minutes or until the chicken is cooked through.

Add the olives, lemon juice, and the remaining herbs to the pan and simmer for another 3 minutes to allow all the ingredients to come together.

Transfer the chicken to a serving platter.  Spoon the sauce over top, sprinkle with sumac, and serve.