2. In a large saucepan, heat 1 tablespoon of olive oil over medium heat. Add the onions, garlic, orange zest and salt. Cook, stirring occasionally, until the onions are slightly caramelized, about 5 minutes. Raise the heat to medium-high, add the mushrooms and cook, stirring frequently, until the juices have almost evaporated, about 10 minutes. Add the tomatoes and their juice, tomato puree and red pepper flakes. Cook over low heat, partially covered, for 15 minutes, stirring frequently to blend the flavors. Stir in 1/2 of the mint.
3. Meanwhile, bring a large pot of salted water to a boil. Cook the pasta until al dente, about 10 to 12 minutes. Drain and transfer to a serving bowl. Toss with the remaining oil. Top with the sauce and sprinkle with the remaining mint.