Bring a large pot of water to a boil and cook 1 pound (453.59 g) cheese tortellini according to the package directions. Before draining, reserve 1/4 cup of the pasta cooking water, then drain the tortellini and set aside.

While the tortellini cooks, melt 1 tablespoon unsalted butter in a large skillet over medium heat.

Add 1 clove garlic, minced, and cook, stirring, until fragrant, about 30 seconds to 1 minute.

Sprinkle in 2 tablespoons all-purpose flour and stir continuously until the flour has absorbed the butter, forms a smooth paste, and begins to smell slightly nutty, about 1 to 2 minutes.

Slowly whisk in 1 1/4 cups (297.5 ml) heavy cream: add a small amount first and whisk until smooth, then whisk in the remaining cream. Add 1/2 teaspoon (0.5 teaspoon) salt and 1/3 cup (33.33 g) grated Parmesan cheese, stirring until the cheese melts. Bring the sauce to a gentle simmer and cook, stirring occasionally, until it thickens, about 5 minutes. If the sauce becomes too thick, thin it with up to the reserved 1/4 cup pasta cooking water, a little at a time, until you reach the desired consistency.

Stir in 5 ounces (141.75 g) baby spinach (thinly sliced) and 7 ounces (198.45 g) sun-dried tomatoes (thinly sliced). Cook, stirring, until the spinach has just wilted, about 1 to 2 minutes.

Add the drained tortellini to the skillet and gently toss or stir to coat the pasta evenly with the sauce. Serve immediately.