To make Red Sauce: In a saucepan, bring tomato purée, water, chili powder, cumin and garlic to a simmer. Simmer for 10 minutes or until thickened slightly. Stir in soy sauce; set aside.
Cover sweet potato in a microwaveable bowl with water; cover and microwave for 5 minutes or until tender. Drain well and mash coarsely; set aside.
In a nonstick skillet, heat oil over medium high heat and cook turkey, onion, garlic, chili powder, oregano, cumin and cayenne for about 8 minutes or until no longer pink inside. Stir in mashed sweet potato.
Divide mixture among pita halves and place in casserole dish. Pour red sauce over top. Cover with foil and bake in preheated 400° F (200° C) oven for 15 minutes. Uncover and bake for about 5 minutes or until sauce is bubbly and pita are slightly golden and crisp.