Bring a large pot of water to a boil. Insert a large fork into the bottom of the cabbage. Holding the fork place the cabbage into the boiling water for about 10 seconds. Remove from water and peel off the leaves. Place the leaves in a large bowl and set aside.
Combine ground beef, uncooked rice, meatloaf seasoning, and eggs. Stir thoroughly; set aside.
Remove cabbage leaves from the bowl and cut off white thick stem part. Line a large oven-safe 9 x 12 baking dish with the smaller inner white cabbage leaves.
Place 2 tablespoons of meat mixture in the center of a leaf. Fold over sides and roll up. Repeat with remaining leaves and meat. Place cabbage rolls seam side down in cabbage leaf lined pan. Cover with chopped onions.
In a small bowl, stir together pasta sauce and diced tomatoes. Pour over onions and cover pan with foil. Bake in preheated oven for 1 hour.