Wash the tomatoes, then cut the cap of, remove the stalk from the cap, remove the kernels with a tea-spoon, then take out the soft pulp. Cut the cap and the pulp into little pieces. Now drip off the tuna. Put it in a bowl and crush it with a cradel.
Put the tomatoepieces and the yoghurt into a bowl and agitate it to a ductile bulk. Wash the cress and cut the leaves off above the bowl of and mix it.
Season the mix with salt, pepper and the horseradish. Put salt, pepper and the tunacreme into the tomatoes