One-Pan Bucatini with Leeks and Lemon

Ingredients

• 1 to 1 1/2 pounds leeks
• 12 ounces bucatini, or other long pasta
• 4 cloves of garlic, thinly sliced
• 1/4 to 1/2 teaspoons red pepper flakes
• 2 tablespoons extra-virgin olive oil
• kosher salt
• freshly cracked black pepper
• 4 1/2 cups water
• Zest of one lemon
• 1/2 cup finely chopped parsley
• Parmigiano Reggiano, for serving, optional