Preheat oven 160°C/320°F.

Separate the eggs.

In the yolk bowl, add sugar. Mix vigorously until well combined.

Add in the oil, milk, lemon juice and salt. Mix in between each of the ingredients until well combined.

Sift in the flour. Whisk in a circular motion until combined, do not over mix. Set aside.

In the bowl of egg whites, add cream of tartar. With an electric mixer, mix on low speed until frothy. Add sugar in 3 batches. Continue mixing on high speed until stiff peaks formed.

Add the egg whites into the yolk batter in 3 batches. Fold in a circular motion until the white disappear, do not over mix. Switch to a spatula and continue folding until combined, do not over mix.

Transfer batter into a 7x7x3-inch pan, greased and lined with parchment paper. Use you spatula to stir and wiggle the batter to release air trapped bubbles.

Bake in preheated oven at 160°C/320°F for 50-55 minutes or until an inserted skewer comes out clean.

Remove the cake from the pans, cool them completely before slicing.

Once the cake is cooled. Slice the cake into 4 sheets, set aside.

In a non-stick pot, add the yolks and sugar. Mix until combined.

Add in the flour, mix until combined. As you’re mixing, gradually add in the lemon juice. Gradually add in to prevent lumps.

Cook the mixture over a low heat. Constantly stir and cook until the mixture is thickened. When you lift up your spatula, it will hold and you’ll notice the curd is translucent. Remove from the heat. Add in the butter. Mix until butter is all melted.

Strain the mixture to prevent lumps.

Cover with cling film directly on top of the mixture to prevent formation of skin.

Refrigerate to cool it completely before using, and while working on the next step.

In a mixing bowl, add in the egg whites and sugar.

Place the bowl over a double boiler on medium low heat. Make sure your bowl is above the water and not touching the water.

Constantly whisk until the mixture reaches 65°-70°C / 150°-158°C. Remove from the heat.

With an electric mixer, mix on high speed until the meringue is stiff and completely cool. This will take about 10-12 minutes. I did mine at about 11 minutes. Use your hand to touch the bowl to ensure that the bowl is completely cool.

Add in the butter in cubes. Make sure the butter is not too soft, just lightly softened and still holding its shape. Add in one a time, continuously until all the butters are added. Half way through adding the butter, you’ll find that the mixture is curdling and liquidy. This is absolutely normal, just keep going. The more butter you add, the mixture will come back together again. The mixture will be stiff and stable.