Grease a 9x 13 inch baking dish.
Cook the egg noodles to al dente as instructed on the package.
Place the sliced onions in a large skillet over medium heat with 2 tablespoons of water. Cook covered for about 10 minutes, until soft and translucent but not browned. Stir frequently and add more water as needed.
Remove the onions from the skillet and add the ground beef. Cook until no pink remains. Drain the fat if needed.
Add the onions back to the skillet with the beef and mix together cooking for an additional 3 minutes.
Put the egg noodles in a large bowl and add the ground beef/onion mixture.
In a medium bowl mix together the diced tomatoes, paprika, dry mustard, brown sugar, salt and pepper.
Stir in 1½ cups of the grated cheese.
Pour the tomato mixture over the noodles and stir gently.
Put the noodle mixture into the prepared baking dish.
Sprinkle the remaining cheese over the top and bake at 350F for 45 minutes.
Serve sprinkled with fresh parsley if desired.