Mix quark, 100 g sugar, milk, oil and salt. Mix flour and baking powder. Add to the quark mixture and work into a smooth dough with the dough hooks of the hand mixer. Grease a deep baking tray (20 x 30 cm) and dust with flour. Roll out the dough to the size of the tin on a well floured work surface and place it inside.
Beat the eggs and 150 g sugar with the whisk of the hand mixer until thick and creamy. Add mascarpone, sour cream, pudding powder and cinnamon and stir in. Spread the mixture evenly on the quark and oil dough and smooth it down. Bake in the preheated oven (electric cooker: 175 °C/ convection oven: not suitable/ gas: level 2) for approx. 1 hour. Cover after 45 minutes if necessary. Take the cake out of the oven and let it cool down on a cake rack for about 2 hours. Clean, wash, halve and possibly seed the grapes. Spread the grapes sorted by colour on the cake. Mix grape juice and cake glaze, bring to the boil and spread evenly on the grapes with a tablespoon.
Cover after 45 minutes if necessary. Take the cake out of the oven and let it cool down on a cake rack for about 2 hours. Clean, wash, halve and possibly seed the grapes. Spread the grapes sorted by colour on the cake. Mix grape juice and cake glaze, bring to the boil and spread evenly on the grapes with a tablespoon. Let dry for 30 minutes