Fill a large pot with water, add a pinch of salt, and bring to a boil. Add spaghetti or linguine and cook according to package instructions for 8-10 minutes. Reserve ½ cup pasta water and drain.

Heat olive oil in a large skillet over medium heat. Add minced garlic and sauté for 1-2 minutes until fragrant and golden.

Carefully add sardines including the oil to the skillet. Break apart with a fork and cook for 2-3 minutes until heated through.

Stir in lemon zest and juice, and red pepper flakes if using. Mix for about 1 minute.

Introduce drained pasta to the skillet. Toss with sardine mixture and gradually add reserved pasta water until desired consistency is reached.

Season with salt and pepper. Garnish with parsley and sprinkle with grated parmesan if desired. Serve immediately.