Make sure carrots, peppers, and onions are grated/chopped and in a bowl ready and waiting.
Add milk, egg, and tomato sauce.
Add your three slices of bread and let sit for about 5 minutes so it can get good and mushy.
Work all ingredients with hands, adding meat as you go until all ingredients and all meat are mashed around together in the bowl. In a seperate bowl, whisk together your ketchup, mustard, and brown sugar. This will be your topping sauce.
Spray one loaf pan (or a few smaller ones) and shape a loaf into the pan. Bake at 350 for 1 hour or until well done. I usually take mine out and drain mine every 15 minutes or so. About 30 minutes into the baking process, take your meatloaf(s) out and spread your sauce on top. It is soo good and tangy!