This is a really easy recipe that I found somewhere on the net and now can't find but it basically went like this.
Cut tomatoes in half and put on a wire rack over a baking tray.
Sprinkle tomatoes with salt, pepper and fresh thyme (helps when you have some growing in the garden!)
Bake in the oven at 150C for 2 and 1/2 hrs until dried on the outside but still soft on the inside.
If you want them firmer than this leave them in for longer.
Take out of oven and leave until completely cool.
Pack in a jar and cover with extra virgin olive oil - I also packed in a few basil leaves also from the garden.