Bring a large pot of salted water to a boil. Add the 12 ounces of cheese tortellini and cook according to the package instructions, usually about 3-5 minutes until they float to the surface and are tender. Once cooked, drain the tortellini and set aside, reserving about 1/4 cup of pasta water for later.
In a large skillet, heat 2 tablespoons of olive oil over medium heat. Add the minced garlic and sauté for about 30 seconds until fragrant but not browned. Stir in the chopped sun-dried tomatoes and cook for 2-3 minutes to release their flavors and soften slightly.
Gradually add the fresh spinach, stirring it into the garlic and sun-dried tomato mixture until it wilts down. Pour in 1 cup of heavy cream, stirring to combine everything smoothly. Let the mixture simmer gently for 3-4 minutes to thicken slightly.
Reduce the heat to low and stir in 1/2 cup grated Parmesan cheese until melted and creamy. Add salt, pepper, and 1/4 teaspoon red pepper flakes if using, adjusting to taste. If the sauce feels too thick, add a splash of the reserved pasta water to loosen it to your desired consistency.
Add the cooked tortellini to the skillet, gently tossing them in the creamy sun-dried tomato and spinach sauce until evenly coated and heated through. Cook for an additional minute to marry all the flavors together.
Remove from heat and garnish with fresh basil leaves for a burst of herbal aroma and color. Serve immediately while warm and creamy.