How to prepare:
1. Preheat oven 180c.
2. Heat brown sugar, 2tbsp butter and 2tbsp orange juice in a pan over medium heat – stirring constantly until butter melts and mixture starts to bubble.
3. Let cool, coat the sides of the pan with cooking spray.
4. Bring 1/4cup orange juice and cranberries to a simmer in a saucepan until about 1/2 the cranberries have popped. Pour over (cooled) sugar mixture.
5. Whisk whole-wheat flour, all-purpose flour, baking powder and salt in a bowl.
6. Separate egg whites and yolks. Put yolks into a large bowl and and add 2tbsp butter, oil, granulated sugar and vanilla. Blend until light and fluffy. Stir in the flour mixture and milk alternately (start and end with flour). Stir until flour is just about incorporated.
7. Beat the egg whites in a mixing bowl until they hold soft peaks. Fold 1/3 of the egg whites into the batter, then fold in the rest. Spread the batter over the cranberries.
8. Bake until the top is golden brown and the cake comes away from the sides of the pan (30-40mins). Let cool in the pan, on a wire rack (15mins). Invert the cake onto a plate. Let cool (at least 30mins) before serving.