Prepare Sauce: Brown (85% lean) ground beef in a deep skillet and then crumble. This does not usually have enough fat to bother draining.
Add to the skillet: the can of drained diced tomatoes, can or jar of spaghetti sauce, Italian seasoning, and salt & pepper to taste. (I use "Hunt's Four Cheese" Spaghetti sauce).
Cover and simmer the sauce on medium-low heat for approximately 25 minutes.
While the sauce is simmering, prepare the box of macaroni and cheese according to the directions on the box. (Hint: It is best to use only just enough milk so that the powdered cheese will dissolve.).
Pour the spaghetti sauce into a 13 X 9 glass baking dish.
Carefully add the macaroni and cheese as a layer on top of the sauce. Do not stir.
In even intervals about 2-3 inches apart, stick a spoon straight down into the dish so that some of the sauce will mix with the macaroni and cheese. Do this going across the pan lengthwise in two rows. Do not stir the entire dish.
Sprinkle the grated cheddar cheese evenly over the top.
Sprinkle Italian bread crumbs over the cheese in a very thin layer.
Sprinkle a pinch of Italian seasoning or Oregano over the bread crumbs.
Bake for 15 minutes or until cheese is melted in a 350 degree oven.
Let stand for 5 minutes and then cut and serve like lasagna squares.