After draining the noodles, dry the pot and place it back on low heat. Add the butter and allow it to melt. While the butter is melting, grate the garlic directly into the pot. Stir the garlic until it becomes fragrant, usually for about 1 to 2 minutes. Then, finely grate lemon zest into the pot according to your preference, and season with freshly ground black pepper. Once the pepper begins to sizzle, pour in 1 cup of the reserved pasta water along with the cooked linguine. Increase the heat to medium-high and toss the ingredients vigorously. As the liquid in the pot reduces, add a few tablespoons of pasta water at a time, continuing to toss vigorously until the pasta is coated in a thick sauce, typically for 1 to 2 minutes.