1. Bring 6 qt. salted water to boil over high heat. Add tortellini, and cook, stirring occasionally, 5 minutes or until tender but still firm to bite. Drain and keep warm.
2. Bring marinara sauce to a light boil in a medium saucepan over medium heat. Reduce heat to low, and stir in cream. Simmer, stirring occasionally, 3 to 4 minutes or until sauce is thoroughly heated. Remove from heat, and stir in 1/2 cup Parmesan cheese, salt, and pepper. Add tortellini, and toss to coat.
3. Grease an 11- x 7-inch baking dish with 1 tablespoon butter. Pour tortellini mixture into baking dish. Sprinkle with remaining 1/2 cup Parmesan cheese, and dot with remaining 2 tablespoons butter.
4. Bake at 350° for 25 minutes or until lightly browned.