Bring a large pot of salted water to a boil. Add bowtie pasta and cook until al dente according to package directions. Reserve ½ cup of pasta water, then drain and set aside.
In a large skillet, melt 1 tablespoon of butter over medium-high heat. Add ground beef and season with 1 tablespoon of Cajun seasoning, salt, pepper, and optional red pepper flakes. Cook until browned and slightly crispy. Remove and set aside.
In the same skillet, reduce heat to medium. Add remaining butter and minced garlic. Sauté for 30 seconds. Add cream cheese and stir until softened.
Slowly whisk in milk or half-and-half to create a creamy base. Stir continuously to avoid lumps.
Mix in grated Parmesan and remaining Cajun seasoning. Simmer for 2–3 minutes until thickened. Adjust seasoning as needed.
Return cooked ground beef to the skillet, then add pasta. Toss everything together, adding reserved pasta water if the sauce is too thick.
Serve hot and garnish with extra Parmesan, chopped parsley, or a sprinkle of red pepper flakes if desired.