Sift the all purpose flour, baking powder and a pinch of salt in a mixing bowl or pan.
Preheat your oven to 180 degrees Celsius/356 degrees Fahrenheit for 15 minutes.
Grease a 7 to 8 inches pan (square, round or heart-shaped) with softened butter or oil. You can also line the pan with parchment paper and then grease the parchment with oil or butter.
In a small frying pan or bowl take a bit more than ½ cup of butter. Melt the butter on a stove-top on low heat taking care not to burn it. Simply melt the butter. No need to heat it.
Measure the melted butter in a steel or glass measuring cup. You need to get about ½ cup of melted butter.
Whip or beat the curd (yogurt) in a medium sized mixing bowl until smooth.
Add water, sugar, apple cider vinegar and vanilla extract to the beaten yogurt.
Briskly whisk using a wired whisk until all of the sugar is dissolved and you get an even mixture.
Sprinkle baking soda on this liquid mixture. Mix thoroughly and evenly.
To the sifted flour, add liquid mixture and the melted butter.
Be quick enough to mix and make a lump free batter. Don’t over do the mixing.
Pour the batter into the greased or lined baking pan.
Shake and tap the sides of the pan on the countertop 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.
Bake at 180 degrees Celsius/356 degrees Fahrenheit for 30 to 35 minutes or more till a tooth pick inserted in the cake comes out clean.
If the cake browns too quickly on the top, then cover the top part with an aluminium foil or parchment paper.
Once well baked, place the cake pan on a wired rack for the cake to cool at room temperature.
Before frosting ensure that the cake is cooled completely.