Share 'Tomato paste that saves over winter'

Hi folks, Does anyone have a recipe for making tomato paste that can be preserved in jars - preferrable without chemical preservatives? I have recipes for chutney and pasatta - but havent got a clue how to make a tomato paste that will save through winter. Surely, its more than just pureed tomatoes???!! Any suggestions greatly appreciated...my mind has gone blank!!! Cheers and thanks, Steph