Slice the steak into thin strips if not already shaved. Shred the provolone and slice the onion.

Bring a large pot of salted water to a boil. Cook fresh tortellini for 2–4 minutes, or frozen for 6–8 minutes until al dente. Reserve 1/2 cup pasta water, then drain.

Heat 1 tablespoon olive oil in a large skillet over medium-high heat. Season steak lightly with salt and pepper. Add steak in a single layer and sear for 1–2 minutes per side until just browned. Transfer steak to a plate.

Add the remaining 1 tablespoon of olive oil to the skillet. Reduce heat to medium and add sliced onion. Cook, stirring, for 5–7 minutes until translucent and starting to caramelize.

Lower heat to medium-low. Pour in heavy cream and stir to deglaze any fond from the pan. Add shredded provolone a handful at a time, stirring until smooth. If sauce seems too thick, loosen with reserved pasta water a tablespoon at a time.

Return the steak (and any accumulated juices) to the skillet. Stir to coat with sauce and warm through for a minute.

Add drained tortellini to the skillet and gently fold until every piece is coated. Taste and adjust salt and pepper.

Plate the tortellini, sprinkle chopped parsley on top, and serve hot.