Using a food processor, pulse together ground turkey, 1/2 of the onion (about 1/2 cup diced), parsley and 1/2 of the All Purpose Lebanese Spice Blend (2 tablespoons) until smooth. If you have trouble getting the mixture to combine, add one or two tablespoons of ice water while pulsing.
Place partially-cooked meatballs in the slow cooker and add in toasted pine nuts, remaining 1/2 cup diced onion, remaining 2 tablespoons All Purpose Lebanese Spice Blend, tomato puree and crushed tomatoes. Stir once to combine then cover and heat on Low for 8 hours or High for 4 hours.
Serve over Lebanese Rice Pilaf with a dollop of plain yogurt on top.
If you don't want to make the All Purpose Lebanese Spice Blend, simply use 1 tablespoon of salt and 2 tablespoons of cinnamon.