In a large pot, bring 4 quarts of water to a vigorous boil. Add 2 tablespoons of salt and spaghetti. Cook for 8-10 minutes until al dente. Reserve 1 cup of pasta water before draining.

In a large skillet, heat 3 tablespoons of olive oil over medium heat. Add minced garlic and optional red pepper flakes, sautéing for 1-2 minutes until fragrant.

Add drained spaghetti to the skillet with the sautéed garlic. Toss and gradually add reserved pasta water to reach desired sauce consistency.

Stir in 1/4 cup of chopped parsley and 1/2 cup of grated Parmesan cheese. Season with salt and black pepper, mixing until cheese melts and combined.

In a small bowl, mix 1/2 cup of softened butter, 3 cloves of minced garlic, remaining parsley, 1/4 cup Parmesan, and optional garlic powder. Adjust seasoning if needed.

Slice Italian bread in half lengthwise and spread garlic butter mixture generously over each half.

Preheat oven to 375°F (190°C). Place bread on a baking sheet, cut side up, and bake for 10-12 minutes until golden and crispy.

Turn on broiler and broil bread for an additional 1-2 minutes until perfectly toasted. Watch closely to avoid burning.

Remove garlic bread from oven, slice, and serve alongside the spaghetti garlic bread, garnished with extra Parmesan and parsley.