The easiest way to get a hot evening meal is to start with a base ( ramen/cous cous/instant rice,instant potatoes) add your protein ( tuna in foil packs, chopped cabanossi or similar, dried mince/cubed meat) and some dried veggies, cheap at your supermarket (peas,corn,carrots,beans,mushrooms)
Add if you like olive oil, dried tomato powder, herbs and spices.
Other foods that are easy to mix and match are hard boiled eggs, hard cheese (will last up to a week not refrigerated) full cream milk powder, salami, Parma ham (my favourite...) beef/fish jerky.
Because dried veggies take a long time to cook (and give you wind if not properly cooked) a good trick is to put them inside a small container (any plastic jar that contained food, like peanut butter, will do ) at lunchtime with some water and by the time you stop for dinner they will be softer. A pinch of baking soda may help.
A good boost of calories is a hot cup of chocolate before you go to sleep. Use the full cream milk powder for that.
Franco