There's plenty of easy stuff that you can portion to fit your needs.
Pasta. Boil water. Dump in however much you want to make with some salt. Wait until soft. Strain. Season with salt+pepper+butter/olive oil+garlic/a sauce if you want to be slightly fancy.
Chicken under the broiler. Get a breast, trim the fat, stick it under the broiler (on a rack near the top) on a
broiling pan for a couple minutes. Pull it out once the juices run clear (poke it with a knife) and the outside is starting to brown with black bits. If you've never broiled before, remember to leave the door ajar, and that it cooks stuff damned quick. You can't really walk away with a timer set for this. Goes good with angel-hair spaghetti because that also cooks really fast.
Baked potatoes. Get a russet tater. Preheat to 425 degrees F. Scrub-wash the tater and
poke holes in it with a fork or w/e if you don't want a spud grenade going off. Rub it with olive oil and salt. Let it bake for ~90 minutes. Cut that sucker open, stick whatever the hell you want inside (cheddar, butter, salt & pepper, veggies, go fuckin' wild).
Roasted vegetables. AKA veggies that aren't tasteless mush. Preheat to 425 degrees F. Rub those suckers with olive oil, sprinkle them with salt and pepper, spread them out on a baking sheet. Stick 'em in until they start to char. You can do this with just about anything you want. If it's something big/thick, cut into strips or whatever, but stuff like asparagus, brussel sprouts, &c. can go in whole.
Foil-baked cabbage. Preheat to 425 degrees F. Take a head of cabbage, cut off the stem, remove the outermost layer or three. Quarter that sucker into wedges (if you're only serving yourself, two should probably do, save the rest). Rip off pieces of foil big enough to completely wrap the wedges, stick 'em in there with the spicing mix of your choice. Some people use olive oil and lemon juice, some use butter and garlic, everyone adds salt and pepper. Find a recipe to suit your taste. Wrap the foil tight around the wedges, put 'em on a baking sheet or on the grill rack, leave them in the oven for your choice (anywhere from 20m to an hour, depending on how tender you want them).
Garlic bread. Get some bread. Cut it into flattish pieces (baguettes and similar work best, but you can do it on Wonder Bread if you're sick and twisted). Spread olive oil and garlic on one side of each piece, maybe a little grated parmesan. Stick those suckers in the toaster for a couple minutes. Bam, done. Eat that shit with your chicken breast and pasta.
That's all shit that's easy, low-mess, and adaptable. Mostly healthy, too.