Preheat the oven to 400ºF.

Chop the asparagus into 2 inch pieces, slice the courgette into ½ cm coins, chop the celery into 1 cm pieces and slice the onion into thin pieces.

Add all of these vegetables and the garlic to an oven-proof baking dish. Drizzle with olive oil and place in the oven for 20 to 25 minutes until tender but not overly cooked.

Remove the vegetables from the oven.

Add the mix to a food processor, along with the lemon peel and 1 cup of water. Blend until evenly combined.

Add a little water, gradually adding more, and keep blending until you get the desired consistency. If you prefer a thin soup, add more water.

Once you have the desired consistency, add the soup mix to a pan, place on the stove top at medium-heat until ready. Season with black pepper.

Drizzle tahini over the top of the soup. Serve alone or with a fresh salad or entrée.