Pat the steak cubes dry with paper towels. Season generously with salt and freshly ground black pepper. In a large skillet or cast-iron pan, heat the olive oil over medium-high heat until shimmering. Add the steak in a single layer, being careful not to overcrowd the pan. Sear for 2-3 minutes per side for medium-rare, or until desired doneness is reached. Remove the steak from the skillet and set aside on a plate, tented with foil to keep warm.

Bring a large pot of salted water to a rolling boil. Add the fettuccine pasta and cook according to package directions until al dente. Before draining, reserve about 1/4 cup of the starchy pasta water. Drain the pasta and set aside.

In the same skillet used for the steak (do not clean it, as the fond adds flavor), melt the butter over medium heat. Add the minced garlic and sauté for about 1 minute until fragrant, being careful not to burn it. Pour in the heavy cream and bring it to a gentle simmer, stirring constantly. Reduce the heat to low. Gradually whisk in the grated Parmesan cheese until smooth and melted. If the sauce is too thick, add a tablespoon or two of the reserved pasta water until it reaches your desired consistency.

Add the cooked and drained fettuccine pasta to the skillet with the Alfredo sauce. Toss gently to coat the pasta evenly. Return the seared steak cubes to the skillet and gently fold them into the pasta and sauce. If the sauce seems too thick, add a little more reserved pasta water. Serve immediately, garnished with fresh chopped parsley and extra grated Parmesan cheese, if desired.