Cook tortellini according to the package. Save ½ cup cooking water before draining.
Brown beef and onion in butter in a deep skillet until the beef reaches 160°F.
Add garlic, Italian seasoning, and pepper. Stir briefly, add marinara, and simmer for 5 minutes.
Lower heat and stir in cream and ¼ cup ricotta until smooth. Turn off the heat and melt in mozzarella and Parmesan.
Fold in tortellini, adding cooking water as needed. Taste for salt, spoon remaining ricotta over the top, and finish with parsley.