Boil the pasta by bringing a large pot of salted water to a rolling boil. Add the pasta and cook according to package instructions until al dente, about 8-10 minutes. Drain and set aside.

In a skillet, cook the bacon over medium heat for about 5-7 minutes until crispy. Remove the bacon and leave the drippings in the skillet.

Sauté minced garlic and diced onion in the bacon drippings over medium heat for about 3-4 minutes until the onion is translucent.

Add butter to the skillet, let it melt, then pour in the heavy cream and let it simmer for 2-3 minutes. Stir in Parmesan cheese and season with salt and pepper.

Combine the drained pasta with the creamy sauce in the skillet, tossing to coat. Add reserved pasta water as needed for consistency and heat together for another minute.

Serve the pasta topped with crispy bacon and chopped parsley, adding red pepper flakes if desired.