Well you may be wondering what's so great about an orange, right? The reason why I chose ORANGE flavor is pretty simple. This recipe, kind of follows the famous middle school experiment. Yes, the volcanic baking soda + vinegar reaction. But yeah, we'll not be using vinegar or soda.
As we all know ORANGE is a citrus fruit and all citrus fruits contain the citric acid which makes them acidic. So here we get our acid.
Now for the base, we'll be using the most commonly used rising agent in baking, the baking powder.
So our reaction is pretty straightforward, the acid in the orange juice combines with the base in the baking powder which gives rise to bubbles. These bubbles help our sponge cake give that airy texture and will help it rise well.

Step 1: Ingredients

YOLK PART
- 4 Egg yolks
- 80 grams of Cake flour
- 3 TBSP Sugar
- Pinch of salt
- 3 TBSP Vegetable oil
- 1 TSP Vanilla flavor
- 3 to 4 TBSP fresh Orange juice
- 1/2 TSP of Baking powder

WHITES PART
- 4 Egg whites
- 1/4 cup Sugar
- 1 TSP fresh Lemon juice

Step 2: The Yolk Part

- Whisk the Egg yolks for a while
- Add the Sugar
- Add a pinch of salt and mix well
- Add the oil and the orange juice and mix again.
- Add the cake flour gradually
- Finally add some food color
- Keep aside

For the cake flour:
- For every cup of all purpose flour, take out 2 TBSP of the flour and add 2 TBSP of cornflour.

Step 3: The Meringue

- Beat the Egg whites till a soft peak stage
- Add the lemon juice
- Beat it again
- Now, very gradually add the sugar.
- Beat until you get a stiff peak stage but be careful not to over beat.

Step 4: Folding

- Now fold the meringue into the yolk part.
- Do it slowly and carefully. Make sure the batter doesn't sit.

Step 5: Baking

- Line your pan with parchment paper
- Pour the batter and tap 2- 3 times
- Bake it for 60- 70 min at 165 degree Celsius.

Step 6: Whip the Cream

- Take some whipping cream in a bowl and start whipping.
- Whip on slow speed until soft peaks form.
- Then whip on fast speed till stiff peaks form. Don't over beat.

Step 7: Icing (Optional)

- Scrape a thin layer from the top and the sides of the cake
- Cut the cake into two slices.
- Prepare some sugar syrup. You could also use fruit juice.
- Now pour the syrup or juice on the cake to keep it moist. Just a little dampness. Don't pour too much.

Now start icing the two layers of the cake with the fresh whipped cream.
I feel icing a cake using ganache is the most easiest and most beautiful way. If your not really good at icing, don't worry. Go ahead and follow this ganache to have a really tempting pastry.
For the ganache:
- Take about 150g of compound chocolate and heat it in a microwave.
- When it melts, add in some fresh cream (about 75 mL)and heat it again till a smooth paste is formed.
- Now simply pour your ganache on your cake and refrigerate. Then serve.

Believe me, this cake pastry tastes really yummy and you should give it a try :)

Step 8: The Science

In this recipe, we separate the yolks and the whites mainly to give airiness to the cake. When we beat the whites, they rise about 4 times due to the trapped air bubbles in the albumen. On folding the meringue with the yolk part, the bubbles hold and release steam during baking which gives a great spongy texture.
Also, Cake flour has lower protein content compared to the normal all-purpose flour which is a result of the bleaching process which breaks down proteins. The low protein content results in light and airy baked goods.

Some reactions that took place:
Oil provides moisture to the cake.

Sugar makes baked goods taste sweet. It also holds the beaten egg whites(meringue).

Eggs act as a binder to hold ingredients together and provide moisture.

Flour adds structure to cake by creating gluten bonds.

The citric acid from orange juice and baking powder release additional bubbles to give a light, airy cake.

References: Instructables - Science of Baking Class

THANK YOU for reading this instructable. If you have any queries you could ask me in the comments section.