Boil the pasta. Bring a large pot of salted water to a boil. Cook pasta until just al dente. Reserve 1 to 1.5 cups of the starchy pasta water before draining.

Sauté the garlic. In a large skillet, warm 2 tablespoons olive oil over medium heat. Add 1 tablespoon butter if using. Add minced garlic and cook 30–60 seconds, stirring, until fragrant. Don’t brown it or it will turn bitter.

Build the light sauce. Stir in a pinch of red pepper flakes if you like heat. Add 1/2 cup pasta water (or a splash of broth) and simmer 1 minute. The starch will start to make it silky.

Toss the pasta. Add the drained pasta to the skillet. Toss to coat, adding more pasta water as needed to create a glossy, loose sauce.

Add greens and Parmesan. Fold in a few big handfuls of spinach. It will wilt quickly. Sprinkle in 1/2 to 3/4 cup grated Parmesan, tossing until it melts and clings to the pasta. Adjust with more water if it gets too thick.

Brighten it up. Grate in lemon zest and squeeze in 1–2 teaspoons lemon juice. Taste and season with salt and black pepper.

Finish and serve. Off the heat, add chopped parsley. Top bowls with an extra dusting of Parmesan and a drizzle of olive oil. Serve warm.