In a large pot, heat oil over medium heat. Add onions, salt and pepper and cook, stirring occasionally, until they become translucent. Add the butternut squash cubes, another few pinches of salt, and stir again.
Let the butternut squash cook for a few minutes, then add the garlic, cumin, coriander, paprika and chili flakes. Stir, then add a splash of white wine vinegar to deglaze the bottom of the pan.
Add the tomatoes, water and quinoa. Cover and simmer until the butternut squash is tender and the quinoa is cooked through (about 40 minutes). Halfway through, I like to taste and adjust seasonings.
When the stew is nearly done, add in a few handfuls of chopped kale. Stir and let it cook until wilted (about 5 minutes more). Taste, and adjust seasonings again. Store leftover soup in the fridge for 45 days or freeze.