I didn't really follow the recipe at all, except as a guide to quantities, but this cake was inspired by this recipe on the King Arthur Flour website. I just loved the idea of candied lemon pieces in the Streusel topping, and blueberries and lemon are a classic combination.
75g butter, melted
Cake - 200g plain flour
2 teaspoons baking powder
250g low fat natural yogurt
115g sunflower oil
1 teaspoon vanilla extract
Pre-heat oven to 180C and line a 12 x 8" (30 x 20cm) shallow baking tin with parchment.
Make the streusel by mixing the melted butter into the other ingredients and leaving to cool. It will be one big lump at this stage, but will crumble nicely when it's cool.
Make the cake by mixing the flour, baking powder and sugar in a large bowl. In a smaller bowl, whisk the yogurt, sunflower oil, eggs and vanilla together until emulsified, then mix into the flour. Don't overmix - just stir briskly until there are no signs of dry flour.
Transfer the batter to the baking tin, then scatter the frozen blueberries evenly over the surface.
Crumble the streusel topping evenly over the surface, then bake for 35-40 minutes, or until a test probe comes out clean. Cool in the tin