Separate the eggs into two large bowls. Add half of the sugar (1 tbsp) to the egg yolk and whisk until it thickens. Add the oil and whisk until it becomes pale. Mix in the yoghurt, and, then, sift the flour and baking powder and lightly mix.

Make meringue: With a different clean whisk, start whisking the egg whites. When the texture becomes loose and it turns white, add the lemon juice and the remaining sugar (1 tbsp), and whisk until you see a stiff peak.

Mix 1/4 of the merengue into the egg yolk mixture, and then gently fold in the rest of merengue without over mixing.