Preheat oven to 170 degrees C. Grease and flour a 20x30cm baking dish.
In a large bowl, cream together 1 cup sugar and 125g butter. Beat in sour cream, vanilla and eggs. Mix in flour, baking powder, bicarb soda and salt. Spread 1/2 the batter into the baking pan. Layer with peaches and top with remaining batter.
In a small bowl, mix 1/4 cup flour, 1/4 cup sugar, pecans and cinnamon. Cut in cold butter until the mixture resembles coarse crumbs. Sprinkle evenly over the batter.
Bake 45 minutes in the preheated oven, or until a knife inserted in the centre comes out clean.