Heat your oven to 200°C/Fan 180°C/Gas 6. Set a large roasting tin on the top shelf to heat up.
Scrub your carrots. Cut into 3-4cm pieces. Tumble into the warmed tin. Gloss with 1 tbsp oil. Season well. Roast for 20 mins till tender and golden at the edges.
Halve, peel and finely chop your onion. Add it to the roasting carrots. Cook for 5-10 mins or till everything is tender.
Scoop the veg into a blender or food processor with 500ml boiling water and your stock cube (or 500ml homemade stock). Chuck in the whole clementine, skin and all. Start blending, trickling the stock in slowly. Whizz in more water or stock till the soup is as thick or as thin as you like it. Season to taste.
Dish up and finish with a drizzle of tamarind over the top.