Get about 2kg of very ripe tomatoes. I like using Plum tomatoes as they have a lot of flesh and the stem is small. Wash them and cut them in half vertically, cut out the stem.

Place the tomato on a box grater skin side outward and grate out all the flesh till you have only the skin left.
(You can always make it EVEN easier and blend with a hand blender with all the skins but for texture, you have to use a few tomatoes chopped finely.)
PS: Don't use tinned tomatoes it doesn't taste good.

Add the yogurt, and rinse out the container with a little bit of cold water. Mix everything together and taste for seasoning. If you have time let it chill in the fridge or add some crushed ice to chill it fast.