Preheat an oven to 300 degrees F (150 degrees C). Line the bottom of a 10-inch cake pan with parchment paper.
Beat the sugar and butter with an electric mixer until light and fluffy. The mixture should be noticeably lighter in color. Add the room-temperature eggs one at a time, allowing each egg to blend into the butter mixture before adding the next.
In a separate bowl, combine the almond meal, cornmeal, baking powder, salt, and lemon zest. Gently fold it into the butter mixture, stirring just until combined.
Pour the batter into the prepared pan and bake in the preheated oven until the cake is golden and a toothpick inserted into the center comes out clean, 90 to 120 minutes.
While the cake is baking, combine the lemon juice and superfine sugar in a saucepan. Bring to a boil over medium-high heat and boil until the sugar has dissolved and the liquid is reduced by half. Remove from heat.
Remove the cake from the oven and use a skewer or toothpick to prick holes in the cake. Pour the lemon syrup over the surface. Allow the cake to cool in the pan completely before serving.