I try to eat relatively low carb (sticking more to the 40% carbs, 30% protein, 30% fat). I also work from home & I'm single, so lunch & dinner are often thrown together when I realize it's getting late & I've been nose-to-the-grindstone for too long.
A few of my go-to staples:
Egg, bresaola & cheese English muffin: I use the 100-calorie high-fiber multigrain English muffins. Although I tried a number of times to cook a muffin shaped egg in a frying pan, I ultimate realized that a Pyrex custard cup in the microwave works better. I do a light grease with olive oil, put the bresaola in the bottom, add 1 egg + about 1/4 cup of egg whites, then top with just a little cheese (for the fat). Microwave ~1m15s at 50%, put on toasted muffin.
I also use the same English muffins with TJ's chicken burgers, a little BBQ sauce and some caramelized onions for a fast lunch sandwich.
I like living grain tortillas (available at Whole Foods) which are higher in protein & fiber. I'll do a quick "quesadilla," though won't always use cheese. I often do refried beans & cooked turkey or chicken with salsa & avocado. I actually find that almond cheese melts pretty well & don't taste completely fake when mixed into a dish, so sometimes I'll use that, too. (It's pretty high in protein, which is a bonus.)
A good brown rice (I prefer Lundberg short grain) can be made in advance and reheats well (covered, steamed to reheat). I'll make a big batch once a week & then mix in:
Protein (poached chicken, leftover beef that's been roasted, grilled salmon, marinated tofu)
Veggies (roast ratatouille that I've made in advance, oven-roasted broccoli, oven-roasted asparagus)
Sauce (ratatouille often needs no additional sauce, otherwise I love a flavorful tomato chutney, which is versatile & healthy without a lot of calories, or a tablespoon or two of teriyaki)