Preheat oven to 350 degrees.
Combine beef, bacon, eggs, bread crumbs, cheese, mayo, Worcestershire sauce, salt, and pepper. Add diced onions if using. If using French fried onions, those get added later (see below).
In a separate bowl, combine ketchup and mustard and mix together. Add 1/4 cup of this mix to the meat mixture. Reserve the rest for the top of the meatloaf.
Press meat into a loaf pan, or shape into a loaf and place in a baking dish.
Spread remaining ketchup/mustard mix on top of loaf. Bake for 50-55 minutes. If using French fried onions, bake for 40 minutes, top with FFO, and bake an additional 10-15 minutes.