To a bowl, add sugar, water and vanilla extract. Mix well.
To the same bowl, add oil and mix.Then sift in, flour, salt and baking powder.Mix until no dry flour is visible. Do not overmix. Spoon batter over caramelized apple. Fill until liner is 2/3 full.
Bake in preheated oven 350oF (180oC), rack in the middle of oven, for 18-20 minutes, or until toothpick comes out clean.
Let cupcakes cool down in pan for 10 minutes. Then, transfer to wire rack to cool completely.