Bring a large pot of water to a rolling boil over high heat. Add 1 tablespoon salt so the water tastes lightly salty.

Cook the twisted pasta for 8 to 10 minutes, stirring occasionally, until al dente with a slight bite. Reserve ½ cup of the pasta water, then drain and set aside.

Place the cubed sirloin in a bowl and season with salt, black pepper, garlic powder, and smoked paprika. Toss until evenly coated so every piece is well seasoned.

Heat olive oil in a large skillet over medium high heat. When the oil shimmers, add the steak cubes in a single layer. Do not overcrowd the pan. Sear for about 2 minutes without moving, then turn and brown all sides for a total of 4 to 5 minutes. Remove the steak to a plate and let it rest.

Lower the heat to medium and add the butter to the same skillet. Let it melt while scraping up the browned bits from the bottom. Stir in the minced garlic and cook for 1 to 2 minutes until fragrant and lightly golden, reducing heat if needed.

Pour in the heavy cream and stir in Cajun seasoning, a pinch of salt, black pepper, and red pepper flakes. Simmer for 3 to 4 minutes, stirring often, until the sauce thickens slightly and coats the back of a spoon.

Remove the skillet from the heat and stir in the Parmesan cheese until melted and smooth. If the sauce is too thick, add reserved pasta water 1 tablespoon at a time until creamy.

Add the cooked pasta to the skillet and toss gently to coat in the sauce. Return the steak and any resting juices to the pan and stir just until warmed through, about 1 to 2 minutes. Garnish with fresh parsley and serve right away.