Bring a large pot of well-salted water to a boil. Cook the refrigerated tortellini according to the package directions, usually 3–5 minutes, then reserve about 1/2 cup of the cooking water before draining.

Pat the shrimp dry with paper towels and season lightly with the kosher salt and black pepper. Dry shrimp brown more readily and are less likely to release excess water into the skillet.

Melt 2 tablespoons of the butter in a large skillet over medium-high heat. Add the shrimp and cook for about 1–2 minutes per side, just until pink and opaque, then transfer them to a plate.

Reduce the skillet heat to medium and add the remaining 2 tablespoons of butter. Stir in the minced garlic and cook for 30–60 seconds, stirring constantly, until fragrant but not browned.

Add the chicken broth or reserved tortellini water, heavy cream, Italian seasoning, and optional red pepper flakes. Simmer gently for 2–4 minutes so the flavors combine.

Stir in the finely grated Parmesan over low heat until melted and smooth. Add the lemon juice, then taste and adjust the salt and black pepper.

Add the drained tortellini and cooked shrimp to the skillet. Toss gently until everything is coated and heated through, adding reserved pasta water 1 tablespoon at a time if the sauce is too thick.

Finish with chopped parsley and additional Parmesan. Serve immediately with lemon wedges so each person can add a fresh citrus finish.