2/3 cup (100g) plain (all-purpose) wholemeal flour
2 teaspoons baking powder
1 cup (280g) greek-style yoghurt, extra
Red wine vinegar syrup
½ cup (125ml) red wine vinegar
¾ cup (270g) honey
Preheat oven to 140°C/280°F fan-forced. Grease and line base and side of a 22cm (8¾-inch) round cake pan, extending the paper 5cm above the edge.
Make red wine vinegar syrup. Bring ingredients to the boil in a medium saucepan over medium heat, stirring, until well combined. Boil rapidly for 5 minutes or until syrupy and reduced to ½ cup (125ml). Pour into cake pan to cover the base. Cool 5 minutes.
Place rosemary sprig in the centre of the syrup. Taking care as the syrup will still be hot, arrange grape halves snugly, cut-side up, in concentric circles starting from the outside of the pan, until syrup is covered.
Beat honey and eggs in a large bowl with an electric mixer on high speed for 8 minutes or until almost tripled in volume. With the motor operating, gradually add oil, then yoghurt and rind, beating briefly just to combine.
Sift flours and baking powder over egg mixture, return husks to bowl. Using a balloon whisk, gently stir dry mixture into egg mixture, taking care not to deflate the mixture. Pour mixture into pan; level surface.
Bake cake, on the lowest shelf, for 1 hour 10 minutes or until a skewer inserted into the centre comes out clean. Stand in pan for 15 minutes.
Cut back the paper collar, then using a tea towel or oven mitts, invert the hot cake onto a serving plate. Cool completely. Serve cake with extra yoghurt.