First sift the all purposed flour/maida with the baking powder and a pinch of salt in a mixing bowl or pan.
Just keep everything ready as you have to be quick enough to mix the batter.
Preheat the oven to 180 degrees c.

Grease a 6 or 7 inches pan with butter or oil. You can also line the pan with butter paper and then grease the butter paper with oil or butter.
Now take some butter and melt it in a small pan or microwave.

Need to get about ½ cup of melted butter. Just melt the butter. No need to heat it.
When the butter is still warm or a bit hot, add the sugar to the melted butter.
Stir and mix well. Keep aside.
Now in a measuring cup or in a small bowl, whisk the 3 tbsp yogurt + 1 tbsp water till smooth.

Add 1 tbsp vinegar. Then add the baking soda and stir.
Pour the butter+sugar mixture, ½ cup water and the frothing yogurt+vinegar+baking soda into the sieved

Add vanilla extract or pineapple essence.
Be quick enough to fold and make a lump free batter. Don’t over do the folding.
Pour the batter in the greased baking pan.
Shake and tap the sides of the pan so that air bubbles are released.

Place the pan in the preheated oven in the center rack.
Keep the heating in both the bottom and top elements of the oven on.