Start by bringing a large pot of salted water to a boil over high heat. Once boiling, add the cheese tortellini and cook according to package instructions, usually around 3-5 minutes, until they float and are tender. Drain the tortellini in a colander and set aside while you prepare the creamy tomato sauce.

In a separate large saucepan, combine the tomato sauce, salt, pepper, dried basil, and minced garlic. Heat over medium heat, stirring occasionally, for about 4-5 minutes, until the mixture begins to bubble and releases a delightful aroma.

While the sauce is bubbling, whisk together the all-purpose flour, milk, and half and half in a separate bowl until smooth. Gradually stir the creamy mixture into the saucepan, ensuring no lumps form. Continue to cook for another 2-3 minutes, allowing the sauce to thicken.

After thickening, reduce the heat to low and add the grated Parmesan cheese, stirring until melted and creamy. Gently fold in the drained tortellini and the julienned baby spinach, mixing carefully to combine and coat everything in the rich sauce.

Once everything is heated through and well combined, remove the pan from the heat. Serve immediately, garnishing with additional Parmesan cheese if desired.