Chop the rhubarb into small cubes, sprinkle with a little sugar, and set aside.
Preheat your oven to 180°C (350°F).
In a bowl, whisk 200 gr of sugar with the egg yolks until pale and foamy.
Add milk, oil, and vanilla essence. Mix until smooth.
Sift in the flour and baking powder. Stir until a thick, creamy batter forms.
Line a baking tray with parchment paper. Pour in the batter and spread evenly.
Distribute the rhubarb pieces on top.
Bake for 15–20 minutes, until the cake is set but not browned.
Meanwhile, beat the egg whites with a pinch of salt until soft peaks form.
Gradually add the remaining sugar and whisk until stiff and glossy.
Remove the cake from the oven and spread the meringue on top.
Return to the oven and bake for another 5–10 minutes, until the meringue is golden and crisp.
Cool completely before slicing and serving.