Combine 1/2 the dill with seltzer, vinegar, 1 tsp coriander, paprika, cumin, salt and pepper in a bowl with lamb and onion wedges.
Heat oil in a 4 qt saucepan over medium heat.
add minced onion and garlic, cook 6-8 minutes.Add remaining coriander, paprika, salt and pepper, prunes, tomato paste and chili flakes, cook until caramelized 2-3 minutes.
Add tomatoes, simmer, cook until thick 15-20 minutes. Add rest of dill , fresh coriander, parsley and juice.
Heat a grill to high, with coals banked on one side, or one burner turned off. Thread onion and lamb onto skewers, cook, turning until desired doneness 15-20 minutes. Put any that are charring to much before being cooked through on cooler area of the grill.