Concassé is the term used to describe a tomato that has been peeled and seeded. This step is important in some recipes, because the skin and seeds can present an unplesant texture, and the juice can make recipes too watery. It is not always necessary, but when it is this easy method makes quick work of it.
To peel and seed tomatoes, cut an X in the end, drop it in boiling water for 30 seconds, then directly into ice water. The temperature shock loosens the skin and it peels right off. To remove the seeds and juice, cut the peeled tomato in half, not from end to end, but through the middle. Squeeze out the seeds and juice as if it were an orange you were juicing. Then dice it up. Voila! Tomato Concassé!