
In a pan, add the blueberries, sugar, lemon juice and water.
In a bowl, cream the butter, oil and sugar until light pale and fluffy.
Add and beat one egg at a time. Add the buttermilk and vanilla into the bowl.
Add a layer of cake batter in the pan, add a layer of blue berry jam.
Repeat the previous step and top with a layer of batter. Smoothen the batter using an offset spatula.
Sprinkle a layer of granulated sugar all over the top of cake batter.
Bake for 40 minutes, check with a wooden skewer to see if completely baked.