Preheat the oven to 170C.
In a clean bowl, whisk in egg yolks, sugar, blackcurrant jam, blackcurrant powder, and blackcurrant concentrate until well combined.
Next, drizzle in water and vegetable oil.
Stir in plain flour, corn starch, and baking powder.
In another clean bowl, whip egg whites and vinegar until frothy. Sprinkle in caster sugar while whipping on high speed until stiff peaks.
Fold in both mixture together and bake it in 6 inch removable round cake pan in the oven for 45 to 55 minutes.
Let it cool upside down.