Pre-heat oven to 350 degrees and spread pine nuts out in a single layer on a baking sheet. Bake until pine nuts are toasted, 5-6 minutes; set aside.
Keep the oven heated to 350 while you prepare the meatballs.
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.
Line two baking sheets with foil and spray with non-stick cooking spray. Scoop the meatballs using a small cooking scoop and divide evenly between both trays. Bake until half-way cooked, about 10 minutes.
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.