This time of year, I eat alone 2-3 nights a week while DH is busy with football refereeing. I like to have what I think of as "component meals." Instead of making a big batch of something, I'll cook a few proteins all at once, like salmon, a chicken breast, and a pork chop. Then I'll have one for dinner and wrap the others up for later. A hearty salad with a grain or bean as the base is really versatile, and you can eat it by itself, over lettuce, with fish or chicken mixed into it, or mixed with other veggies, and it will keep for several days in the fridge. While you're making this, you can also make extra of the grain or bean and use it as a hot side dish. A typical football night meal for me would be a bed of lettuce with a pre-cooked piece of chicken cut up, and a scoop of bean salad, with maybe some avocado or sunflower seeds.
If you cook bigger batches of things, think about how they will taste as leftovers, or if they can be repurposed later. A roast chicken might seem silly for a single person, but it will make a delicious dinner with a couple simple side dishes, and you'll have protein for the week to use for soup, sandwiches, salads, burritos, whatever! Not to mention this is way cheaper.