1. 1. Begin by bringing a large pot of salted water to a boil. Add the tortellini and cook according to the package instructions until al dente. Drain the tortellini and set it aside.

2. 2. In a large skillet, heat the olive oil over medium-high heat. Add the beef, season with salt and pepper, and cook until browned on all sides, about 3-5 minutes. Remove the beef from the skillet and set it aside.

3. 3. In the same skillet, melt the butter over medium heat. Add the minced garlic and sauté for 1-2 minutes, until fragrant and lightly golden.

4. 4. Stir in the diced tomatoes, beef broth, Italian seasoning, and red pepper flakes (if using). Simmer the mixture for 2-3 minutes, allowing the flavors to meld.

5. 5. Add the cooked tortellini, seared beef, and fresh spinach to the skillet. Gently toss everything together until the spinach wilts and the dish is heated through.

6. 6. If desired, sprinkle the Garlic Butter Beef and Spinach Tortellini with grated Parmesan cheese. Serve the dish hot and enjoy every delicious bite!