Preheat oven to 180 degrees C. Line a baking tray with baking paper.
Toss carrots in 1 tbsp of the olive oil, season with a little salt and roast for 40 minutes, turning halfway through.
About 10 minutes before the carrots are done, preheat the remaining olive oil in a large saucepan over medium heat.
Add the celery and onion and cook until translucent (around 4-5 mins). Add the minced garlic, turmeric and cook off for about 1 minute. Season with salt and pepper.
Add the roasted carrots, butter beans and stock. Bring to the bioil, reduce heat and simmer for 30 minutes.
5 minutes before the end, add the tahini and stir to combine. Adjust seasoning if necessary.
Turn off the heat and add the lemon juice. If you like a smooth texture use a stick blender until the soup is creamy. For a more rustic texture use a potato masher.
Serve and top with herbs of your choice. Parsley, basil or coriander works well.