Pre-heat oven to 170°C fan bake. (340°F)
Melt together butter and white chocolate in the microwave in 30 second bursts. Stir.
Add sugar and lemon zest & juice, stir again and add in the eggs.
Sift in the flour and baking powder.
Fold everything together and whisk out any lumps.
Pour into a lined slice tin.
Bake for 22 minutes until blondie feels firm on the surface. Allow to cool before cutting into squares.
Dust with icing sugar and serve.
