Boil orange in a pressure cooker (cook in low flame till one whistle) or in a saucepan put 2 cups of water and orange. Boil it for 60 minutes covered in low flame.
After boiling allow orange to cool down completely. Then remove its pulp and remove pith from the skin.
Dry roast coconut powder over medium heat on a nonstick for 5 minutes stirring continuously.

When it turns into little brown switch off the flame and keep it aside to cool down completely before adding.
Dry Ingredients: Shift whole wheat flour, baking soda, baking powder, salt twice and keep it aside.
Wet Ingredients: Now add boiled orange, curd, sugar, oil with custard powder in a grinder until smooth.

Now mix wet ingredients with dry ingredients, and roasted coconut powder (3/4 cup). Mix them well.
Put batter into a greased pan. Sprinkle 1/4 cup of coconut powder over prepared cake batter and with help of spatula press gently.

Tab the cake pan on a countertop to release any large air bubbles.
Put cake pan into the preheated pressure cooker and bake it for 1 hour.

Tips:

Adjust sugar according to your taste.
Baking time may vary.
If cake batter looks dry, add 2- 4 tbsp of curd.
If baking in Oven: Bake in the preheated oven at 180 deg Celsius or around 360 Fahrenheit for about 1 hour. The baking time may vary. So keep checking the cake after 40 to 45 minutes.
For best results use orange with thin skin.
“Malta” orange is perfect for this cake.

Pressure Cooker Method:
Grease the baking tin with oil and dust it by sprinkling whole wheat flour over greased surface evenly. Pour the mixture into the greased baking tin.

Important Notes:

Use the baking tin of 6 inches in diameter, so that it can easily get into the pressure cooker.
Use a 5-liter pressure cooker. It should be big enough to hold the baking pan.

Baking Tin should be made of Aluminium.
If baking tin comes into direct contact with the base of the pressure cooker, it can burn (overbake) the cake. So use pressure cooker container which has big holes in it or any aluminum small stand.
No gasket and whistle are needed. Remove them before baking.
Don’t add water to the pressure cooker.

How to Bake In A Pressure Cooker?

Heat the pressure cooker on high heat for 2 minutes. Use sea salt or sand as a layer inside a cooker. Put a steel stand on a layer of salt or sand.
Now put the cake tin containing the cake batter (Do not put water inside the pressure cooker).
Close the pressure cooker lid and do not put the whistle on the lid. Remove the gasket (rubber ring) from the lid.

Lower the flame after 2 minutes. Let it bake for 50 -60 minutes on low flame. After 60 minutes check cake with a knife, if the mixture does not stick, it means the cake is done.
If batter still sticks to knife then again bake for another 10 minutes. Do not open the lid immediately.
Eggless Pressure Cooker Cake is ready.