Pat the steak dry with paper towels and season both sides generously with salt and black pepper. Let it sit at room temperature for 15-20 minutes while you prep the other ingredients to ensure even cooking.

Bring a large pot of salted water to a boil and cook the cheese tortellini according to package instructions until al dente (3-4 minutes for fresh, 7-8 minutes for frozen). Drain well, reserving 1 cup of pasta water for sauce adjustment if needed, and set aside.

Heat olive oil in a large skillet (at least 10-inch) over medium-high heat until shimmering. Add the steak and cook for 3-4 minutes per side for medium-rare doneness (130°F internal temperature). The steak should have a golden-brown crust. Remove from the pan and tent loosely with foil to rest for 5 minutes.

Reduce heat to medium and add butter to the same pan used for steak. Once melted, stir in minced garlic and cook for about 30 seconds until fragrant, taking care not to burn it. Pour this garlic butter into a small bowl and set aside.

In a separate saucepan, combine heavy cream, milk, and grated Parmesan over medium heat. Stir continuously until the cheese melts and the sauce thickens slightly, about 3-5 minutes. The sauce should coat the back of a spoon. Season with salt and pepper to taste. If the sauce is too thick, thin gently with reserved pasta water a splash at a time.

Gently toss the cooked tortellini in the Alfredo sauce to coat every piece evenly, creating a creamy, cheesy pasta.

Slice the rested steak thinly against the grain. Drizzle the garlic butter from the pan over the steak slices, then plate alongside the cheesy Alfredo tortellini. Sprinkle chopped fresh parsley on top and serve immediately.