Preheat the oven to 180°C. Grease and flour a baking tray of approx. 30 × 40 cm. Put the sugar, vanilla sugar, salt and grated lemon zest (of the previously washed lemon) in a small bowl. Mix and set aside.
Mix the flour with the soluble oat flakes and baking powder in another bowl and set aside.
Beat the eggs with the sugar mix until light and fluffy. Add the oil drop by drop, continuing to whisk. Add the liquid cream drop by drop as well. Then add the mix of flour and oat flakes. Blend with an electric whisk just long enough to remove any traces of flour. Add the milk and grappa and briefly blend with an electric whisk. Transfer the batter to the baking tray and spread evenly.
Wash and dry the Val Venosta apricots, pit them and place the apricot halves on the entire surface of the cake. Sprinkle with plenty of granulated sugar and bake for approx. 25 minutes. Do the toothpick test to check the baking. Remove from the oven, allow to cool and serve.