Presoak a clay pot, top and bottom, in water for 15 minutes.
Slice the eggplant, unskinned, very thin and set aside, brown the finely chopped onion in the olive oil until transparent.
Put the tomatoes, pesta, and salt into a blender container and blend. To this mixture add the onions and remaining olive oil.
In the presoaked pot, place alternate layers of sliced eggplant