1. Bring a large pot of water to a boil, add 2 teaspoons salt, and cook spaghetti until al dente; drain and reserve 1/2 cup pasta water.

2. Heat olive oil in a large skillet over medium heat and brown the ground beef, crumbling as it cooks; drain excess fat.

3. Stir in onion and cook until translucent, then add garlic and cook until fragrant.

4. Season beef with Italian seasoning, 1/2 teaspoon salt, and black pepper.

5. Pour in marinara sauce, bring to a gentle simmer, and cook 5 to 7 minutes to meld flavors.

6. Reduce heat to low, add Velveeta cubes, and stir until completely melted and silky.

7. Stir in milk to loosen the sauce; add red pepper flakes if using.

8. Add the drained spaghetti to the skillet and toss, adding splashes of reserved pasta water as needed so the sauce coats every strand.

9. Taste and adjust seasoning with remaining salt and more pepper if needed.

10. Serve immediately topped with Parmesan and basil if desired.