Peel and finely chop the onion. Put it with the olive oil and butter in a soup pot over medium-high heat. Sauté, stirring occasionally, until the onion turns a rich golden color, about 5 minutes.
While the onion is sautéing, cut the zucchini into ½-inch chunks. When the onion is done, put in the zucchini and sauté until it begins to brown, 10 to 15 minutes. Sea