You can make a simple tomato sauce (saute onions, garlic and herbs with skinned chopped tomatoes and a little sugar - simmer for an hour or two until required concentration consistency is achieved) and hot-bottle this in sterilised, airtight jars. I use jam jars from my local cookshop and the dishwasher on hottest setting to sterilise the jars and lids. It keeps for up to two months and I only had one furry jar out of a dozen or so. Hygiene is paramount so avoid sneezing, dirty hands and utensils. I should also point out that I have the constitution of a hyena, for those with more delicate tummies home-preserving may be unadvisable.