Bring a large pot of salted water to a boil. Add spaghetti and cook according to package instructions until al dente.

Reserve 1 cup of pasta water, then drain the pasta in a colander.

In a large skillet, heat the olive oil over medium heat. Add minced garlic and red pepper flakes, sautéing until fragrant, about 1-2 minutes.

Add the drained pasta to the skillet, tossing to coat in the oil and garlic mixture. If the pasta seems dry, add reserved pasta water a little at a time.

Stir in the chopped parsley, salt, and black pepper. Toss well to combine.

Serve immediately, garnished with additional parsley and grated Parmesan if desired.