Bring a large pot of salted water to a rolling boil, then add the pasta and cook until just al dente, about 8 minutes. Drain, reserving a cup of pasta water, and set aside.
While the pasta cooks, heat olive oil in a large sauté pan over medium heat until it shimmers and smells fruity and fragrant.
Add the finely chopped garlic to the oil and cook gently, stirring constantly, until fragrant and golden, about 30 seconds to 1 minute. Be careful not to burn it.
Stir in the peas and cook for another minute until warmed through and bright green, watching for a slight pop or snap as they heat.
Zest the lemon directly into the pan, then squeeze in the juice, stirring to combine. The mixture should brighten and smell citrusy.
Add the drained pasta to the pan with the peas and lemon sauce. Toss gently to coat the noodles evenly, adding a splash of the reserved pasta water if needed to loosen the sauce.
Sprinkle the freshly grated Parmesan over the pasta, then season with flaky sea salt and freshly cracked pepper to taste. Toss everything together until glossy and well mixed.
Let the pasta rest for a minute in the pan to absorb flavors, then serve immediately in warm bowls, garnished with extra lemon zest and cheese if desired.