1. Bring a large pot of salted water to a boil. Add the tortellini and cook according to package instructions until al dente, usually about 3-5 minutes for fresh or 7-9 minutes for frozen. Drain and set aside, reserving about ¼ cup of pasta water.
2. While the pasta cooks, heat 1 tablespoon of olive oil in a large skillet over medium-high heat. Season the sliced steak generously with salt, pepper, and half of the Italian seasoning. When the oil is shimmering, add the steak in a single layer. Sear for about 2 minutes on each side until browned but still tender. Remove steak from pan and set aside.
3. Lower the heat to medium, add the remaining tablespoon of olive oil to the same skillet. Add minced garlic and sauté for about 30 seconds until fragrant—don’t let it burn! This step brings out the deep garlic flavor that I love in this dish.
4. Add the halved cherry tomatoes (if using) and cook for 2-3 minutes until they begin to soften, releasing their juices.
5. Pour in the beef broth or water, scraping the bottom of the pan to loosen any flavorful bits left from the steak. Let it simmer for 2 minutes to reduce slightly.
6. Toss in the cooked tortellini and baby spinach. Stir gently to combine, letting the spinach wilt from the residual heat.
7. Return the sliced steak to the pan, sprinkle with the remaining Italian seasoning, and stir to distribute everything evenly. If the mixture looks dry, add a splash of the reserved pasta water to loosen the sauce.
8. Remove from heat and stir in the grated Parmesan cheese until melted and creamy. Taste and adjust salt, pepper, and red pepper flakes if you want a bit of kick.

A quick note from my kitchen: I like to slice the steak thinly before cooking to speed up the process and make every bite tender—this is a trick that saved many of my early kitchen experiments from turning into chewy disasters!