Peel the tomatoes. You can do this by carefully cutting an x across the bottom of the tomato, cut only the skin, no deeper, and carefully place the tomatoes into a pot of boiling water for 1 minute. Then place them into a bowl of ice water. After they cool, remove the skins by hand. They will peel away easily.
Cut the tomatoes into small pieces. Put them in a large pot and bring them to a boil and then let them simmer for 10 minutes.
Pour into a fine mesh colander to strain out the liquid. (reserve the liquid for other recipes!)
Place the drained tomatoes in a blender and blend well.
Place the blended tomatoes in a smaller size pot and cook on a low simmer until all the water is evaporated, roughly 15-25 minutes, while stirring constantly.
Once you feel that the tomatoes are turning into the paste you add coarse salt and mix very well.