Rinse and dry the basil thoroughly to avoid water diluting the pesto. In a food processor, combine basil, pine nuts, garlic, Parmesan, lemon zest, and lemon juice. Pulse while streaming in olive oil until the mixture emulsifies into a smooth, slightly coarse sauce; taste and season with salt and pepper.

Toast the pine nuts in a dry skillet over medium heat until fragrant and golden, about 2–3 minutes, shaking the pan constantly. Stir half the toasted nuts into the pesto for texture and reserve the rest for garnish.

Bring a large pot of salted water to a rolling boil and add pasta. Cook until just shy of al dente—usually 1–2 minutes less than the package recommends. Reserve about 1 cup of pasta water before draining.

Pat shrimp dry and toss with olive oil, salt, pepper, and optional red pepper flakes and lemon zest. Let sit for 10 minutes while the grill or pan heats.

Preheat grill or grill pan to high. Cook shrimp 2–3 minutes per side until opaque with a light char and firm to the touch.

Return drained pasta to the pot over low heat. Add several tablespoons of pesto and a splash of reserved pasta water, tossing until the sauce evenly coats the noodles. Adjust consistency with more water or pesto.

Use a ring mold or fork to mound pasta into neat stacks on plates. Top each stack with 3–4 grilled shrimp, sprinkle with toasted pine nuts and fresh herbs, and finish with a drizzle of olive oil and extra lemon zest.