Sieve Whole wheat flour, baking soda and salt together and keep aside.
To it add Brown sugar and mix with a spatula until it is evenly combined.
In a wide dry bowl, add milk, Vanilla extract and vinegar and mix well.
Combine dry ingredients to the wet ingredients and gently fold with a spatula. Do not over mix the cake batter.
Take a ½ to 1 teaspoon of sifted whole wheat flour and sprinkle on to the washed ,dried grapes. Coat evenly so that they do not sink bottom of the cake . Fold the black grapes into the cake batter gently using spatula.
Preheat your oven to 170°C . Grease your cake mould with flavourless oil and dust with whole wheat flour twice. This helps cake sticking to the mould or pan. Transfer the cake batter immediately in the silicon mould (can use any cake pan )and level the top with the spatula .
Bake in the preheated oven at 170°C for 35 to 40 minutes or inserted skewer comes out clean. Have an eye after 30 minutes as every oven behaves different.
Let it cool completely before serving.
Garnish with black grapes sprinkle with confectioners and serve with hot cup of coffee or milk.
Notes
Sieve dry ingredients for at least three times.Wash grapes and pat dry on towel .When adding dry ingredients to wet ingredients gently fold the cake batter using cut and fold method. Do not overmix.Preheat oven to 170°C and bake immediately when transfer to cake mould.You can use any cake mould. I used Silkomart silicon cake mould.Sprinkle a teaspoon of dry ingredients on to the black grapes and mix thoroughly . It helps the fruit to get evenly distributed to the cake and do not sink bottom of the cake too.