Line a 9” round cake tin with baking paper and grease lightly.
In a large bowl beat the yolks and sugar until smooth, light and thick. Add the oil, vanilla, baking powder and lemon zest and mix until it forms a homogenous mixture.
Add the ground almonds and fold until incorporated.
In a separate bowl whisk the egg whites with a pinch of salt until it forms soft peaks. Add two tablespoons of sugar and continue beating until it forms a stable meringue.
Gradually fold the egg whites into the rest of the ingredients, about two tablespoons at a time, ensuring not to over-mix.
Pour the batter into the baking tin and optionally scatter the sliced almonds on top.
Bake at 170°C for 30 minutes until the top is lightly golden browned.
Serve with whipped cream, or slice in half and frost the middle with whipped cream.