I just made this and I feel an urge to share since it came out so well and was laughably easy.
Cook in about 3 cups water (I guess using stock would be even nicer):
--about a cup of red lentils
--about half a small cabbage, finely shredded
When it's soft (around 15 minutes) add about 2 cups of good tomato sauce and warm it all together.
I used my own homemade sauce (straight from the freezer), which is Marcella Hazan's Tomato Sauce II, basically onions, celery, carrots, tomatoes, olive oil, and salt, but you could use anything that tastes good.
Season. I added some salt and pepper. That's it.