I have an issue with tomato paste.
Many of my recipes calls for 1 or 2 tbsp of tomato paste. I open a can. use 1 or 2 tbsps, put the remainder in a plastic container. Then the next time I need tomato paste there is mold growing on top of the tomato paste.
A few times I split the remainder in two plastic containers and froze one. So it's not quite as wasteful.
Some stores have tomato paste in a tube. like toothpaste. I haven't found any around here but they sell it at amazon so I ordered some. it's more expensive than in the cans but I think maybe it will be cheaper in the long run - with less waste.
Tubes are definitely more expensive, around $2 to $4 per 4.5-ounce tube versus $0.80 to $1.50 for a 6-ounce can. But once a tube is opened, it’ll last 30 to 45 days without deteriorating in flavor. Tomato paste from a can will start to get moldy far faster because it’s exposed to more air, so you’ll have to freeze the excess if you want it to last.