Preparation

• Combine the cilantro, oil, pistachios, lime zest and juice, garlic, and 3/4 tsp. salt in a blender or food processor, and purée until smooth. (The pesto may be made up to 2 days ahead; cover and refrigerate if not using within a couple of hours. Bring to room temperature before tossing with the pasta.)
• Prepare a medium-high (400°F to 475°F) charcoal or gas grill fire. Grill the poblanos, turning occasionally, until well charred and tender, 14 to 16 minutes. grill the corn, turning occasionally, until charred in places. Brush each onion slice with a little olive oil and grill, turning occasionally, until tender with some grill marks, about 8 minutes.
• Transfer the poblanos to a bowl, cover, and let sit until cool enough to handle, about 20 minutes. Transfer the onion and corn to a cutting board.
• Meanwhile, bring a large pot of well-salted water to a boil.
• Rub off the poblano skins, remove the stems and seeds, and cut into 1/2- to 3/4-inch pieces.
• Using a serrated knife, cut the kernels from the corn cobs, keeping them in planks as much as possible. Peel the onion slices, if necessary, and then coarsely chop.
• Cook the pasta according to package directions until al dente. Drain and return to the pot or transfer to a large bowl. Add the pesto, poblanos, onion, half of the corn, and half of the cheese, and toss well. Serve topped with the remaining corn, cheese, and some cilantro leaves.