Bring a large pot of salted water to a boil and cook the cheese tortellini according to package directions; drain and set aside.
While the tortellini cooks, melt the butter in a large skillet over medium heat.
Add the minced garlic and cook, stirring, until fragrant, about 1 minute.
Sprinkle in the flour and stir until it forms a paste and begins to smell nutty, about 1 minute.
Slowly whisk in the heavy cream, smoothing the sauce as you go; then add the salt and grated Parmesan and simmer until slightly thickened, about 5 minutes.
Stir in the sliced baby spinach and sun-dried tomatoes and cook until the spinach wilts, about 1–2 minutes.
Add the drained tortellini to the skillet and gently toss to coat evenly with the sauce; serve immediately.