Generously butter an 8-inch round cake pan. Set aside.
In a large mixing bowl, whisk together the milk and yeast. Gradually whisk in the cornmeal, flour, sugar, eggs, and lemon zest. Whisk until the ingredients are well blended.
Turn the batter into the prepared pan. Let rest for 30 minutes.
Preheat the oven to 350°F.
Sprinkle the top of the batter generously with sugar. Bake for 40 minutes until browned. Let the cake cool completely, then turn it out of the pan. Serve with lightly sweetened whipped cream.