Prepare the Semolina Mixture: In a saucepan, combine milk, water, butter, salt, and citrus peels. Bring to a boil, then remove peels. Gradually whisk in semolina, cooking until thickened. Let cool.
Mix the Batter: In a separate bowl, beat eggs with sugar until light. Add ricotta and vanilla, mixing until smooth. Incorporate the cooled semolina mixture.
Bake: Preheat oven to 350°F (175°C). Grease and line a 9-inch (24 cm) springform pan. Pour in the batter and bake for about 1 hour, until golden and set.
Cool and Serve: Allow the cake to cool completely. Dust with powdered sugar before serving.
