Buy the bigger portion.
That may sound opposite to your diet plans.
But the next time you go out to dinner be sure and order the larger portion. As soon as it arrives ask for a box, split it in half and save the portion in the fridge for lunch the next day.
Saves time because new you don’t have to make yourself lunch the next day and saves money as it is usually more cost effective per ounce to buy the full meal and not the lunch portion.