This recipe (from How to Cook Everything) is fairly easy, and the results smell and taste a lot like lasagna (yay!), but without the hassle of boiling/wrangling noodles or the long bake time. The original recipe calls for sauteed ground meat, which you could do if you want, but the way I made it was all vegetables (plus chickpeas and cheese), and it was very filling and satisfying. In the original Bittman recipe he implies that you can used cooked leftover... anything in this (meat or vegetable), and I'm inclined to agree. Also he says it can be assembled up to a day in advance before baking, which is helpful.
4 cups of your favorite tomato sauce*
1/4 cup water or veggie stock
2-3 pounds of whatever veggies you like (2-3 pounds uncooked if you're going to roast them for this recipe, or about 3-4 cups of already cooked leftover veggies/beans/etc)
1 roasted pepper, seeded peeled and chopped (optional - I didn't have one, but it seems like it would be good)
1/2 cup couscous (whole wheat or regular) (I think you could substitute fine bulgur or quinoa if you are gluten free, without any adjustment to the recipe except maybe a slight increase in stock/water; or other heartier grains you'd want to par cook first, and maybe measure about 1-1 1/2 cups of cooked grains)
1/2 to 1 cup of cheese (I used feta and parmesan) (amount to taste and dictated by what you have on hand - goat cheese would be fun too I think, but feta and parmesan were a great combination)
First, preheat the oven to 400, and cut up your veggies (if you're not using up already-cooked leftover veggies) into smallish chunks or slices. I used sliced zucchini and summer squash and a drained can of chickpeas. You could use things like diced eggplant, winter squash, carrots, peas, any cooked beans, etc. Whatever you choose, if it needs cooking, cut into small and roughly equal pieces, put it on a big baking sheet, drizzle with oil and salt and pepper, and roast till things start to brown, 10-15 minutes or so. I think greens might be good in this - you could sautee (or blanch, drain/squeeze out) and chop chard, spinach, or kale and mix it in with the roasted veggies once they're out of the oven.
Heat your tomato sauce along with the stock or water in a large-ish saucepan until bubbling (I maybe used a bit more than 1/4 cup stock). Stir in the roasted bell pepper if you have it and the couscous, stir, cover, and remove from the heat. Reduce the oven temperature to 350.
Oil a 2 quart baking dish (not metal), and layer the couscous/tomato mixture alternating with the roasted veggies and cheese, till you fill the dish (if you're using leftover pre cooked vegetables, I'd recommend warming them up a bit before layering them, so they don't slow down the baking.
Bake at 350 for 20-25 minutes until the sauce is bubbling and the cheese is melty. Cool a bit before serving. This was great with a green salad on the side.
It also made delicious leftovers (the flavor might even improve!) with a fried egg and sriracha on top.
*easiest tomato sauce I make:
1 onion, chopped
as many garlic cloves as you like (4 or so), chopped
a 32 oz can of crushed tomatoes
whatever seasoning you like (basil, oregano, parsley)
salt and pepper
fry the onion and garlic in oil until softened (you could chop a carrot very small for this too if you wanted). Add the can of tomatoes and a little water if it seems thick. Add herbs and salt and pepper to taste and simmer over medium low heat for 20 minutes.
EVEN EASIER: Trader Joe's sells 32 oz cans of Marinara Sauce which I was shocked to find is pretty decent tasting. Actually, they sell several different kinds - look for the kind that has the shortest ingredient list (it's impressively short).