Sift the ricotta and mix it with a wooden spoon until smooth.
Add the potato starch, raw cane sugar, egg yolks, grated lemon zest and lemon thyme leaves. Finally gently fold in the two whipped egg whites.
Heat the oven to 180°C, butter a 24 round cake pan, dust with potato starch and scrape in the batter.
Bake for about 50 minutes, until golden and firm. Let cool then unmould onto a serving dish.
In the meantime, wash the peaches, slice them and cook them with lemon juice, sugar and vanilla for 5 minutes, then spoon them with their sugar onto the cake.