M&S do a couple of versions of cheese rarebit in a ceramic dish - I put that in the oven with a part baked bread roll (and if I'm feeling gourmet, I add a handful of chopped scallions over the top once it's cooked). That used to be my "go to" with a glass of white wine when DH was away once I'd got DD to bed - then she learned about it and uses them up in the afternoons after school!!
Lidl bacon lardons (they come in a double pack and last weeks) tossed into a dry pan (plenty of fat comes off the bacon), add a sliced onion and some sliced mushrooms. Mix an egg with some cream if you want sauce, and add to the pan once turned off the heat - although just a scattering of grated parmesan can be enough.. Serve with some fresh pasta which only needs 3 minutes to cook.
I freeze any bits of leftover cauliflower cheese - and then reheat those in the oven while cooking a lamb chop (throw it on a baking tray for 15 minutes - put a sprig of rosemary underneath it if feeling gourmet!) and roasting a couple of baby potatoes (halved) or a regular potato chopped into 1-2cm dice (if I have thought ahead enough, I will peel/slice potato in advance (night before or in the morning), whether regular or baby, and throw into a Ziploc bag with olive oil, pepper and some garlic granules).
If no cauli cheese, this can work just as well with a couple of cherry tomatoes in the baking tray for last 10 minutes, or some diced mediteranean veggies (onion, garlic, pepper, tomatoes, mushrooms, courgette etc) - these can also be diced and marinating in advance, and frozen both before and after cooking (useful to throw into a baking tray straight from frozen, or to defrost the cooked leftovers and use as the basis of a pasta sauce with just some tomato sauce or even just passatta).
Another nice one, not huge effort for one, is the baby roast potatoes or diced potatoes with feta stuffed chicken. Under the skin of a part boned chicken breast, put a pinch of thyme leaves and about 75-100g chunk of feta cheese - season on top with salt and pepper and a drizzle olive oil. Roast for 40 minutes (plenty of time for a decent G&T while folding socks!). I usually have diced med veg with that too.
Into a piece of tinfoil, put a salmon darne, about a quarter sliced onion, thinly sliced carrots, and some cubed potatoes. Season, add a splash of white wine (or water), seal your tinfoil packet and bake for 20 minutes.
Stop en route home for nice fresh crusty bread (loaf, baguette or just a decent roll), 2 nice slices of ham from deli counter and small tub of proper coleslaw and make a decent sandwich. (Some sundried tomato pesto and a good strong cheddar in place of the coleslaw is also great - and can be toasted to melt the cheese).
Tub of hummus and either breadsticks or carrot sticks (HM or packet bought for "steaming"). Or small tub pate with crackers.
Handful of olives and a couple of slices of parma ham or some nice salami, cherry tomatoes, maybe a slice of cheese and some crackers etc. M&S do small portion packs of nice meats that live weeks in the fridge. Various combinations of nice cold nibbly things can work well, and be varied enough over time to not get bored.
A lamb shank put in a low temp oven (150 degrees) on the timer for a couple of hours before you get home, maybe with a jacket potato sitting with it, can be an effortless option.