1. Heat oil in a large Dutch oven over medium-high. Add onion; sauté 5 minutes. Stir in salt, paprika, turmeric, and garlic; cook 1 minute. Add carrots; cook 1 minute. Stir in stock; bring to a boil. Reduce heat to medium-low; cover and simmer 20 minutes or until carrots are very tender.
2. Combine carrot mixture and 3 tablespoons tahini in a blender. Remove center piece from blender lid (to allow steam to escape); secure lid on blender. Place a clean kitchen towel over opening in lid (to avoid splatters). Process until smooth. Divide soup evenly among 4 bowls. Drizzle 2 teaspoons Tahini Sauce over each serving. Top each serving with 1 1/2 tablespoons pistachios and 1/2 teaspoon oregano leaves.