Yo. This soup is not easy breezy lemon squeezy at first. But once you get a handle on the parts and what you want the soup to be for you, you'll be able to eyeball it & make it whenever you have a languishing cup of cooked beans or split peas in your fridge that you want to use up, or some bell peppers (not green ones, even I can't help you with that). You have to want an excuse to get out multiple roasting pans and heat up your kitchen. When you're done, I encourage you to make it a meal with the addition of cooked farro, amaranth, and quinoa and a swirl of baby spinach if that's you're thing. But don't be afraid to play around and make it slightly simpler - no beans, fewer or zero carrots, and veggie broth instead of cashew milk makes for a fiery first course or side. If you add more things, I think you'll lose the specificity of the flavors...but I wouldn't stop you. I've thought about roasting a turnip when I don't have cooked beans on hand, but have yet to try it.
half or 1 tbsp each coriander and cumin seeds
2 yellow or orange bell peppers (I'm fairly confident that red would be fine, please don't waste your time with green ones)
1.5 tbsp butter or earth balance, olive oil would be fine although less creamy
1 bay leaf
1 c cooked white beans or split yellow peas in their cooking liquids (optional) (extra note: I usually cook white beans with onion powder, garlic powder, and za'atar / split yellow peas with ginger and garlic - don't be afraid of using non-plain beans if you think they'll go well with the flavor profile of the soup)
1/2 c veggie broth (may need another cup if not using beans in their liquids)
1/2 c cashew milk (may need more - if you want a very creamy soup, replace veggie broth with cashew milk, especially if not using butter)
Turn oven to 400, hotter if that's what it takes to roast your vegetables. Put the peppers on one rimmed pan with a little olive oil. You do not need to peel your carrots - that is the only unfussy part of this recipe, yay. Chop carrots into pinky-sized rods and roast on separate sheet with a few glugs of olive oil + shakes of salt + the cumin seeds and coriander seeds, tossing to coat. Pop everything in oven, shake pans/toss carrots and turn peppers every 10 min. Things will likely be nicely browned in 30-40 min.
While the roasting is happening, peel and chop onions. Heat butter in big soup pot, turn heat down to medium-low, and add onions and bay leaf. Add a little water and more butter and turn heat down if things are sputtering/browning too early - you want low and slow to caramelize in ~30 min. Remove bay leaf if you are worried you will forget to do this later.
Add roasted peppers (remove stem, deseed if you don't like spicy things), carrots, seeds, and beans with their cooking liquid (if using) to onions. Pour veggie broth and cashew milk over pans to get ahold of any lingering seeds/yummy roasting juices, and then transfer liquids to soup pot. Add more broth/milk if needed to submerge vegetables/beans. Simmer 5-10 min, remove bay leaf (THIS IS VERY IMPORTANT). Blend using immersion blender, or wait to cool slightly and transfer to blender in batches.
Taste. It is probably delicious, but may need a little more salt and/or a lemon squeeze if it isn't quite acidic enough. Leftovers will likely want a squeeze of lemon.
You can make this a meal by mixing in cooked grains (I like a combo of farro, amaranth, and quinoa with this), some extra beans/split peas, and baby spinach.