It turned out with a mixture of sweet and tangy, and the cake itself had the consistency of a sponge cake. I liked the fact that it wasn't too sweet and the flavor of the orange juice seemed to brighten the blueberries. I did not add in the oatmeal, but may substitute part of the flour with oatmeal when I make this again. I made it for dessert but I think it would be just as good at the breakfast table served as a muffin with fresh fruit and cup of hot coffee. Here is what I did:
1 tbs sugar
1/3 cup Self-rising flour
Place 2-3 tablespoons of blueberries into a microwave safe mug or ramekin. If frozen, defrost berries before adding the rest of the ingredients. Stir in 1 tablespoon of sugar. Add 1/3 cup of self rising flour and a dash of cinnamon. Add the orange juice in a tablespoon at a time, stirring in between each addition. Add by the tablespoon until mixture is a thick batter. Microwave for 1 minute or until toothpick inserted in center comes out clean. Sprinkle top with powder sugar. Serve warm.