Cook the spaghetti in salted boiling water according to package instructions until al dente.
While the pasta cooks, heat olive oil in a large skillet over medium heat.
Add minced garlic and red pepper flakes; sauté for about 1 minute until fragrant.
In the skillet, add the shrimp, cooking until they turn pink, about 3-4 minutes.
Stir in the lemon zest and juice, followed by the broth; bring to a simmer.
Once the pasta is cooked, reserve 1/2 cup of pasta water and drain the rest.
Add the drained pasta to the skillet, tossing to combine with the shrimp and sauce.
If the mixture seems dry, add reserved pasta water a little at a time.
Season with salt and pepper to taste.
Serve hot, garnished with chopped parsley and grated Parmesan cheese.