A bright, garlicky linguine tossed with tender Swiss chard in a lemony, olive-and-caper sauce, finished with Parmesan and parsley. Light yet deeply savory with perfectly balanced acidity and umami.
Zest the lemon, avoiding the white pith, then juice it and set both aside (about 1/4 cup juice).
Bring a large pot of salted water to a boil. Cook the linguine until al dente according to package directions. Reserve 1 cup pasta water, then drain.
In a food processor, combine the green olives, capers, caper brine, lemon zest, and lemon juice. Pulse to a rough paste, scraping the sides as needed.
Heat the olive oil in a large skillet over medium heat. Add the diced onion and cook until very soft and golden on the edges, about 10 minutes. Stir in the minced garlic and red pepper flakes; cook until fragrant, 1 to 2 minutes. Add the chopped Swiss chard and cook until it begins to wilt, about 2 minutes.
Add the cooked pasta, butter, the olive-caper mixture, and 1/2 cup reserved pasta water to the skillet. Toss to coat. Sprinkle in the sea salt and grated Parmesan; toss again. Drizzle in more reserved pasta water as needed to evenly coat the noodles. Stir in the chopped parsley. Taste and season with black pepper and more salt if needed. Garnish with additional Parmesan.