Start by cutting your beef sirloin steak into small, bite-sized cubes. Thinly slice the sweet onions to ensure they cook evenly and caramelize nicely. Shred your cheddar cheese if it’s not pre-shredded. Having everything ready before you start cooking will make the process smooth and enjoyable.
Bring a pot of salted water to a boil and add the shell pasta. Cook according to package instructions until al dente. Drain and set aside, reserving a small amount of pasta water in case you need to loosen the sauce later.
Heat one tablespoon of olive oil in your large skillet over medium-high heat. Add the cubed steak and sprinkle with salt, pepper, and garlic powder. Sear the steak cubes until browned on all sides but not fully cooked through — about 3-4 minutes. Remove the steak from the pan and set aside.
In the same skillet, add the remaining tablespoon of olive oil. Toss in the thinly sliced sweet onions and cook over medium heat, stirring occasionally, until they turn golden brown and sweetly caramelized — around 10-12 minutes.
Return the seared steak cubes to the skillet with the caramelized onions. Pour in the beef broth and stir everything together, letting it simmer for 2-3 minutes to blend the flavors and finish cooking the steak.
Stir the cooked shell pasta into the skillet. Sprinkle the shredded cheddar cheese over the top and gently mix until the cheese melts and coats the pasta and steak mixture. If needed, add a splash of the reserved pasta water to achieve a creamy consistency.
Sprinkle chopped fresh parsley on top for a pop of color and fresh flavor. Serve your Steak & Sweet Onion Cheddar Shells hot and enjoy the perfect combination of savory steak, sweet onions, and melty cheese in every bite.