Bring a large pot of salted water to a boil. Cook rigatoni until al dente, about 10-12 minutes. Reserve 1/2 cup pasta water before draining.

Heat a large skillet over medium-high heat. Season steak with salt and pepper, sear for 4-5 minutes each side, then let rest.

In the same skillet, reduce heat to medium, add butter until bubbly, then add minced garlic and sauté for 1-2 minutes.

Slice steak and return to skillet with garlic butter. Warm through for 1-2 minutes.

Add drained rigatoni, toss to combine. Add reserved pasta water if needed for creaminess.

Finish with parsley and optional parmesan and red pepper flakes. Serve hot.