Preheat your oven to 180 °C (ca 356 °F). Grate the zest of 2 lemons.
In a large bowl, work the ricotta with a spatula until creamy.
Add the eggs and sugar and mix well between each ingredient, mashing with the spatula to avoid lumps.
Sift the potato starch and vanilla powder (or add the vanilla extract if using) into the bowl. Mix until fully incorporated.
Fold in the grated lemon zest.
Line a 20 cm diameter round cake pan (8 inch) with parchment paper extending above the rim, then fill with the batter.
Bake for 40 minutes or until the ricotta cake is set, and the surface becomes dark, almost burnt. The crunchy top crust is the characteristic of this cake, imparting a delicious caramel aroma.
Let the cheesecake cool in the pan on a wire rack. Once it reaches room temperature, refrigerate it for at least 4 hours, preferably overnight. This helps the flavors to meld and the cheesecake to set properly.
To serve, remove the ricotta cake from the springform pan and slice.