Bring a large pot of salted water to a boil and cook the cheese ravioli according to package directions; drain and set aside.
While the water boils, season the cubed sirloin with 1/2 tsp salt and black pepper.
Heat olive oil in a large skillet over medium-high heat and sear the steak cubes until browned on all sides; remove steak from the pan and set aside.
In the same skillet, melt butter and add the chopped onion, cooking until translucent.
Add the minced garlic and cook for about 1 minute until fragrant.
Deglaze the pan with 1/4 cup beef broth, scraping up any browned bits from the bottom.
Pour in the remaining beef broth and heavy cream, bringing the mixture to a gentle simmer.
Stir in the Parmesan cheese until melted and the sauce begins to thicken.
Add the cooked steak and ravioli back into the skillet, tossing gently to coat in the sauce.
Top with fresh parsley and serve immediately.