Rigatoni with Chunky Vegetable Sauce

2 tablespoons extra-virgin olive oil
1 medium yellow onion, diced medium
2 medium zucchini, diced medium
1/2 pound cremini or button mushrooms, trimmed and quartered
2 garlic cloves, minced
1 can (28 ounces) tomato puree
Coarse salt and ground pepper
2 tablespoons fresh oregano leaves, coarsely chopped
1 pound rigatoni

In a medium pot, heat oil over medium-high. Add onion and cook until translucent, about 5 minutes. Add zucchini and mushrooms and cook until vegetables soften slightly, about 4 minutes. Add garlic and cook until fragrant, 30 seconds. Add tomato puree, season with salt and pepper, and bring mixture to a boil. Reduce heat to a rapid simmer and cook until zucchini is crisp-tender, about 8 minutes. Stir in oregano.
Meanwhile, in a large pot of boiling salted water, cook pasta until al dente. Reserve 1 cup pasta water; drain pasta and add to sauce, tossing to combine and adding enough pasta water to create a sauce that coats pasta. Serve immediately.

Source: http://www.marthastewart.com/340648/rigatoni-with-chunky-vegetable-sauce?czone=food/dinner-tonight-center/dinner-tonight-main-courses¢er=276948&gallery=274485&slide=339113