Preheat the oven to 350 degrees F. Scatter the pecans on a rimmed sheet pan and toast until they are fragrant and a shade or two darker, 7 to 8 minutes. Cool.
Bring a large pot of salted water to a boil. Add the pasta to the boiling water and cook according to the package directions until al dente. Drain, reserving about 1/2 cup pasta water.
Meanwhile, put the pecans in a food processor with the lemon zest, basil, parsley and garlic and pulse six or seven times to make a chunky paste. Scrape down the sides of the work bowl and, with the processor running, add the olive oil in a steady stream to make an almost-smooth pesto.
Scrape the pesto into a large serving bowl and stir in the cheese. Season with salt. Add the spaghetti and toss, adding the reserved pasta water to loosen, if needed.
Photograph by Kana Okada
Courtesy of Food Network Magazine