Using two sauce pans, put 1 Tbs butter and 1 Tbs olive oil in each pan, over a medium-low heat. 

Put half the onion in each pan and cook until it is a golden color. 

Add half the ground beet to each saucepan and cook till it has lost its raw color.  Crumble the beef as you stir. 

Add salt and black pepper. 

Add the tomatoes to one of the pans. 

Once this pan starts to boil, reduce the heat to a light simmer. 

Cook until the tomatoes have reduced and seperated from the butter.  This will take about 40 minutes.  This is your sauce. 

Cook the meat in the other pan for just a few minutes after it has lost its raw color.  Remove from the heat. 

Put this meat in a mixing bowl. 

When this meat is cooled, add the mortadella, egg, nutmeg, ricotta, and 3/4 cup of grated cheese. 

Mix well.  This is your filling. 

Add about 6 Tbs of the balsamella sauce to the meat filling, mixing well. 

Cover the bottom of a baking pan with a thin layer of balsamella sauce.  Once you stuff the manicotti place them in a single layer in the pan. 

Stuff the manicotti with the meat filling. ( See note)

Cover the top of the manicotti with the meat sauce and the rest of the balsamella sauce, make certain that all the pasta is well covered. 

Sprinkle the remaining cheese over the top. 

Bake at 400F for 15-20 minutes, or until a light golden crust forms on top. 

Remove from oven and let rest for 10 minutes before serving. 

Note: One of the easiest ways to stuff manicotti is to place the filling in a resealable plastic bag, cut off a corner (about 1 inch).  This make a nice bag that you can use to squeeze the filling into tubes of pasta.