This fast and delicious soup is equally delicious served hot or cold. You can also easily adapt the flavors - use cilantro and cumin for a Latin American flair, or some coconut aminos, a touch of miso, and sesame oil for an asian adaptation. I like to serve this with a poached egg and some crispy prosciutto for a full meal. Adapted from a recipe by J. Kenji López-Alt at Serious Eats.
Heat the oil in a large pot over medium high heat then add onion with a pinch of salt. Cook over medium high heat, stirring often until the onions are soft and translucent but not browned, about 5 minutes. Add the garlic and cook until fragrant, another minute. Add zucchini and stir to mix. Add the stock and bring the mixture to a simmer.
Cook at a simmer for 10 minutes, until the zucchini is just soft but still bright green. Turn off the heat and remove pot from the burner. Add the basil and purée the soup until smooth. Season to taste with salt, pepper, and lemon juice.