Spaghetti with Scallion Sauce

Ingredients:
• 1 lb spaghetti
• 1/3 cup olive oil
• 4 cups chopped scallions (from 4 bunches)
• 2 garlic cloves, finely chopped
• 1 teaspoon finely grated fresh lemon zest
• 3/4 teaspoon salt
• 1/2 teaspoon black pepper
• 1 oz finely grated Parmigiano-Reggiano (1/2 cup)
Directions:
• Cook spaghetti in a 6- to 8-quart pot of boiling salted water until al dente.
• While pasta cooks, heat 3 tablespoons olive oil in a 12-inch heavy skillet over moderate heat until hot but not smoking, then cook scallions and garlic, stirring occasionally, until scallions are softened and garlic begins to turn golden, about 5 minutes • Transfer scallion mixture to a blender and add zest, salt, pepper, remaining olive oil, and 1/2 cup pasta-cooking water, then purée until smooth. (Use caution when blending hot liquids.)
• Drain pasta in a colander and return to pot.
• Toss pasta with scallion purée, cheese, and salt and pepper to taste over moderate heat until pasta is well coated.
Source: http://www.epicurious.com/recipes/food/views/Spaghetti-with-Scallion-Sauce-232616#ixzz1WGqiNWwv