Have all chopped and sliced ingredients ready beforehand.
Bring water with 3 tablespoon salt to a boil and add the pasta. Cook for 10-12 minutes and set aside, saving the pasta water.
Heat olive oil on pan and add garlic. Toss gently for 30 seconds and add hot pepper flakes, salt and pepper. Cook and toss for 30 seconds.
Add parsley, cooked pasta, pasta water and squeeze the half lemon. Stir and bring to boil. Add fresh pepper and salt and toss the mixture gently.
Turn off heat and let mixture rest for 30 seconds to thicken a bit.
Serve warm with freshly grated parmesan.