Heat the oven to 320°F (160 °C). Beat the eggs and sugar well, pour the oil in a thin trickle and add the water.
Sift the flour with baking powder and vanilla, pour it into the mixture in parts, stirring constantly. Put in the jam and stir the dough nicely. Pour this into a greased tray and bake on the middle element of the oven for 20-30 minutes.
Allow to cool. Serve the cake sprinkled with powdered sugar and cut into diamond shapes.