Bring a large pot of water to the boil. Add sweet potatoes and cook for about 5 minutes, or until tender. Drain and set aside.
While the sweet potatoes are boiling, heat 1 tablespoon oil in a large pan over medium-high heat. Cook the onion and green capsicum until tender. Season with cumin, salt and pepper.
In a large bowl, toss together the sweet potatoes, onion mixture and cooked turkey. Heat remaining 2 tablespoons oil in a large pan over medium heat. Place the sweet potato mixture in the pan; flatten with a large spoon or spatula and cook until the bottom is crisp. Carefully turn and cook the other side until crisp. Serve warm.