Divide thawed bread dough into 6 pieces and roll into balls. Saute onion in a large saucepan until browned; add beef and cook until beef loses its red color (overcooking beef will cause Runzas to be very dry). Stir in cabbage and MSG, cover and steam until cabbage is wilted.
Preheat oven to 350 degrees F (175 degrees C).
Remove beef/cabbage mixture from heat and let cool. Roll each dough ball into a 5 x 5 inch square. Fill center of each square with about 1/2 cup of beef mixture. Bring opposite corners of dough square together and seal. Place smooth-side-down on a lightly greased cookie sheet and flatten slightly.
Bake in preheated oven for 20 to 25 minutes. Remove from oven and butter top of each pastry as soon as they come out of the oven.