0,5 kg sugar
1 oz (two tablespoons) fresh lemon juice
a big pinch of salt
a sprig of fresh thyme
Blanch the tomatoes for half a minute in boiling water. Then peel & core them, and drop them into a large, heavy jam-making pot.
Add the sugar, lemon juice, salt, and branch of thyme. Bring to a simmer, then a steady boil, stirring every few minutes. Watch the jam closely, the water cooks off and the juices become syrupy: you’ll need to stir it steadily to make sure it doesn’t stick to the bottom of the pan.
Squash any big chunks of tomato while you’re at it. Skim off any sticky foam that forms on the surface, too, since those dense little bubbles will cloud the jam’s sparkle later. The jam will begin to set up in about 25 to 35 minutes.
When it’s softly set, remove the thyme and ladle the jam into clean hot jars and seal.
Canning tips: http://yourspanishrecipes.blogspot.com.es/2013/08/canning-tips.html
Make it spicy only adding few chillies while stead boiling. Taste great with creamy cheese and foie.