Preheat the oven to 180℃ (160℃ fan)/350°F/gas mark 4. Lightly grease a 20cm (8inch) square cake tin.
Beat together the butter and caster sugar until light and fluffy.
Add the eggs one at a time and beat well. Add the yogurt, lime zest and milk
Add the plain and wholemeal flour, and the bicarbonate of soda and gently fold in. Spoon into the prepared tin and level the top. Arrange the raspberries on top and gently push down into the cake mixture a little way.
Bake for 45 minutes or until springy to the touch and beginning to pull away from the edge of the pan.
To make the topping:
Stir the granulated sugar and lime juice together and spoon over the cake whilst still hot. Allow to cool slightly before turning out onto a wire rack to cool completely.
Serve cut into squares.
Nutrition information is approximate and is meant as a guideline only.