Blueberry Traybake with Lemon Streusel

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.

To keep the cake low(ish) in saturated fat, I used my standard recipe for a yogurt and oil cake, although I did keep the butter in the streusel topping. I read on one of the blogs featuring the same cake that there was an awful lot of streusel crumbs, so I reduced it to a half quantitiy, then wished I hadn't, as it didn't cover the blueberries well enough and the cake rose around the little lumps of streusel. I also made the streusel  by my favoured method of melting the butter and mixing it with the other ingredients - this ensures the streusel isn't powdery at all.

This was a really good cake, and it would also make a tasty dessert if served still warm. It was very moist from the blueberry juice and the little pockets of crunchy lemon streusel gave a lovely contrast in flavour and texture. What started off as a potential problem - not enough streusel - ended up being a positive feature of the cake! It was also just the right size for the four of us to eat in two days - one problem with fresh fruit cakes is that they don't keep long, especially in the sort of unexpectedly hot weather we're having at the moment.

Ingredients

Streusel - 75g plain flour

50g light muscovado sugar (or demerara for more crunch)

2 tablespoons finely chopped candied lemon peel

a few drops lemon extract

grated zest of half a lemon

75g butter, melted
Cake - 200g plain flour
2 teaspoons baking powder

200g caster sugar

250g low fat natural yogurt
115g sunflower oil
3 eggs
1 teaspoon vanilla extract

200g frozen blueberries

Method
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