Set a large soup pot over medium heat. Add the cumin and coriander seeds to the pot and toast, stirring them up often. Toast the spices until very fragrant, about 45 seconds to a full minute. Dump the seeds out onto a small plate and allow them to cool completely before grinding up to a powder in a spice grinder. Set the ground spices aside.
Return the large soup pot to the stove over medium heat and pour in the olive oil. Swirl the oil around a bit and then add the onions to the pot and stir. The onions should be sizzling, but on the quieter end of sizzling. Lower the heat if necessary. Keep cooking the onions, stirring occasionally, until very soft and translucent (but not browning), about 7-8 minutes.
Add the ground cumin and coriander to the pot, along with the ground chillies as well. Stir and cook along with the onions for one full minute. Then, add the minced garlic and ginger to the pot and stir. Keep cooking until the garlic is very fragrant, about 1 minute.
Add the carrots to the pot along with big pinches of salt and pepper. Stir the carrots to coat them in the spices and sautéed onions. Then, add the red lentils to the pot and stir once more. Finally, pour in the vegetable stock and give it a final stir.
Bring this broth-y carrot, lentil, and spice mixture to a boil and then lower your heat to a simmer. Simmer this mixture uncovered, stirring here and there, until the carrots are quite soft, about 30 minutes.
Carefully ladle the broth-y carrot, lentil, and spice mixture into the pitcher of an upright, vented blender. To this mixture, add the tahini, sesame oil, and Tamari. Close the lid on the pitcher and slowly bring the speed of the blender up to high. You may have to add a few splashes of water to get things moving. Blend until you have a completely smooth puree.
Pour the spicy sesame carrot soup back into the pot. At this point, you can leave it as-is or add some water to make the texture a bit more fluid. I personally like a bit of fluidity in pureed soups, so I added 2 cups of water at this point. Bring the soup up to a boil, stirring often. Stir in the lemon or lime juice.
Give the soup a taste at this point to see if you need to adjust some of the seasoning. Maybe it needs even more lemon/lime for your taste, some extra pepper etc. Adjust the seasoning to your liking and then serve! I topped mine with chopped cilantro, drizzles of tahini and chili oil, and sesame seeds.
The pureed soup will be super thick when it comes out of the blender. Some people enjoy soup this way! If that’s you, leave it at that. For me, I like a pureed soup to have some fluidity to it. I ended up adding 2 full cups of water to mine to get the texture that I like.
If you don’t have the whole spices on hand, you can use an equal amount of ground cumin and coriander and skip that initial toasting and grinding step.
Really take your time with cooking the onions. It’s a key flavour-building step for this simple soup.
I was able to blend the entire soup in one go with my old Vitamix 5200 series blender.
This spicy sesame carrot soup is hearty with lentils and tahini, and flavourful with chilies, whole spices, toasted sesame oil, and slowly cooked onions. Simple ingredients and easy to make!