Preheat oven to 350oF (180oC). Oil and line pan with parchment paper (6 inch;15 cm diameter. Set aside. To a bowl, add sugar and water. Whisk until sugar is completely dissolved.
Then add oil and vanilla extract and mix well.
Sift in flour and baking powder.
Mix until dry flour is no longer visible. DO NOT OVER MIX (mix until dry and wet ingredients are just combined).
Transfer batter to pan. Top with sliced peach.
To a another bowl add flour and sugar for the streusel top. Mix well
Then add oil and mix until crumbly.
Sprinkle the streusel over peaches, making sure to spread it at evenly as possible.
Bake in preheated oven to 350oF (180oC), rack middle position, 50-55 minutes, or until toothpick inserted in the middle of cake comes out clean.
Let cake cool down in pan for 10 minutes. Then transfer to wire rack to cool down completely.