I find soups work pretty well and they’re easy to cook then freeze or just keep in the fridge for a few days. The options are pretty much endless.
Get a broth boiling in a pot, choose your protein source of choice (chicken, beef, lamb, whatever) throw that in first, whatever veggies take your fancy and if you want to crank up the carbs a bit, dump in some brown rice (just put it in raw and let it boil up with the soup), or try potato, sweet potato, pasta or whatever you like.
Once everything is in the pot, stick a lid on, turn the heat down a bit so it’s just simmer and let it go for half an hour, stirring occasionally.
Options are endless and it’s an easy way to get down a shitload of food if you’re trying to keep the calories up.