-8 oz dry rotini pasta (3 cups measured dry)
-4 tbsp salted butter, divided
-1 cup diced onion
-2 cloves garlic, minced
-2 1/2 cups frozen peas
-1/3 cup pasta water
-zest from 1 lemon, juice from 1/2 lemon, plus more for serving
-1 cup freshly grated parmesan, plus more for serving
-Salt and pepper (fresh cracked preferred)