Start off with some fresh tomatoes. In this case, I used on the vine small tomatoes. Wash, cut in half, drizzle with olive oil and sprinkle with salt. Cook at 250f approximately 4-5 hours (depending on your oven or whatever factors).
The flavor ended up being very concentrated and delicious. I imagine you can store them in olive oil if you don't use them up right away...but don't hold me to that. Botulism may come a'knockin.