Ready to bake a simple sponge cake with just four everyday ingredients? This easy 4-ingredient sponge cake recipe makes baking a breeze.

Start by pre-heating your oven to 350 Fahrenheit, and lining the bottom of a 9-inch cake pan with parchment paper. Leave the sides of the pan ungreased.

Use a medium bowl of a stand mixer or electric mixer (you can also use a hand mixer) with the whisk attachment. Whip on medium-high speed the eggs and sugar until they triple in size, for around 3 minutes.

It is key to whip the eggs to just the right volume and no more. If it's whipped too hard and it becomes stiff, it won't rise as it should.

When you start whipping, you will see your eggs are fluffy and white but still pourable. Then, a few moments later, the mixture will be stiff enough that you won't be able to pour, but it won't be stiff enough that it holds a stiff peak.

Fold in flour into the egg mixture using a spatula. Gently mix it into the wet ingredients until just combined, being careful not to overmix and keeping the batter light and fluffy. This is to avoid popping the air bubbles created by whipping the eggs.

Fold in the melted butter, the same way you did with the flour. Pour the batter into the pan, and immediately place it in the oven to bake. Bake for 30 to 40 minutes, until a toothpick inserted in the middle comes out clean and your cake looks golden brown.

Remove the sponge cake from the oven, place over a wire rack, and let cool for 5 minutes. Then, invert the cake tin into the cooling rack and remove the parchment paper from the bottom of the cake. Leave the cake to completely cool upside down on the wire rack, for around 2-3 hours.