Tahini yogourt: In a bowl, whisk together Astro Original yogourt, tahini, parsley, lemon juice, oil, salt and pepper until smooth.
In a bowl, beat egg with 2 tbsp cold water. Stir in bread crumbs, onion, garlic, lemon zest, mint, salt, pepper, allspice and cinnamon. With your hands, mix in lamb and feta. Wetting hands if necessary to prevent sticking, form balls of 2 tbsp each; place on a foil-lined baking sheet. Bake in 400°F (200°C) oven until digital thermometer inserted sideways into the centre of a few balls reads 160°F (71°C), about 20 minutes.
Meanwhile, wrap pita halves in foil and warm in 400°F (200°C) oven for 15 minutes. To assemble, place 1 pita half on each plate; spread some yogourt mixture on top and mound with spinach. Top with meatballs; drizzle with more yogourt mixture. Sprinkle with tomatoes.