Sieve whole wheat flour, baking powder and baking soda in a plate or tray. Keep aside.
Melt butter in a pan.
Once the butter has melted, place the pan on the countertop. To the melted butter, add sweetened condensed milk.
With a wired whisk, stir and mix very well. The whole mixture should be homogeneous and even.
Then add warm milk. You can warm the milk in a small pan on the stove top or in the microwave.
Next add sugar and begin to stir with a wired whisk, till the sugar is dissolved completely.
Add vanilla extract or powder or scraped vanilla bean.
Add all sieved dry ingredients to the wet ingredients.
With a wired whisk mix lightly and with light hands. Don’t use pressure from your hands while mixing. Mix evenly. If there are tiny small lumps in the batter, then its fine.
Pour the cake batter in the prepared pan.