Fill a large pot with 4 quarts of water, add salt, and bring to a rolling boil. Add spaghetti and cook for 8–10 minutes until al dente, then drain, reserving 1 cup of pasta water.

In a large skillet, heat olive oil over medium heat. Add minced garlic and red pepper flakes, sauté for 1–2 minutes until garlic is fragrant.

Add drained spaghetti to the skillet, tossing in the garlic oil. Gradually pour in reserved pasta water, mixing until spaghetti is coated.

Reduce heat to low, fold in parsley and Parmesan. Season with salt and black pepper to taste, stirring until cheese melts.

In a small bowl, blend softened butter, minced garlic, and parsley. Optionally add garlic powder. Mix until well-integrated.

Preheat oven to 375°F (190°C). Slice Italian bread in half and spread garlic butter generously over cut sides.

Place garlic bread on baking sheet and bake for 10–12 minutes until golden brown and crispy.

Serve spaghetti alongside garlic bread, optionally sprinkling more Parmesan and parsley on top.