Heat oil in large skillet over medium heat. Cook onion and garlic about 3 minutes or until onion is tender. Stir in turkey, tomatoes, lentils, cumin, and chili powder. Cook 5 minutes, stirring occasionally. To serve, spoon about ¼ cup meat mixture into each taco shell. Top with sour cream, romaine, cheese, avocado and radishes, as desired.