Preheat the oven to 400°F/200°C. Line a large baking tray with baking paper.
Put the sweet potatoes on the lined tray. Drizzle the oil over and sprinkle the chipotle powder and salt. Coat the potatoes in the oil, toss them with your hands. Flatten them on the tray and bake them until they are tender and the edges are brownish, about 15-20 minutes.
Make the tahini. Put the tahini ingredients in a cereal bowl. Whisk until you get a creamy soft paste. If the texture is too thick, add lemon juice or water. If it's too runny, add 1 tablespoon tahini.
Serve the sweet potato on a large plate. Drizzle over the tahini and tomato puree, and garnish with parsley (be generous with the parsley. It adds freshness). Enjoy!