Season the steak pieces generously with salt and black pepper, then heat olive oil in a large skillet over medium-high heat until shimmering. Add the steak bites in a single layer and sear for 2-3 minutes until deeply browned on all sides but still medium-rare inside.

Transfer the seared steak to a clean plate and reduce heat to medium. Add 1 tablespoon of butter to the same pan and sauté the minced garlic for 30-45 seconds until fragrant.

Pour in the beef broth, scraping the bottom of the pan with a wooden spoon. Add the Italian seasoning and bring the liquid to a simmer.

Add the tortellini directly to the simmering broth, stirring gently to coat. Cover and cook until the pasta is nearly tender, about 3-4 minutes for fresh tortellini or 5-6 minutes for frozen.

Uncover and stir in the remaining 2 tablespoons of butter and the grated Parmesan cheese. The sauce will begin to thicken and turn creamy.

Return the steak bites (and any accumulated juices) to the pan and gently fold everything together until warmed through, about 1-2 minutes more.

Stir in the chopped parsley and taste for seasoning, adding more salt and pepper if needed. Sprinkle in some red pepper flakes for heat if desired.