To make the custard: In a medium saucepan, beat the sugar and the egg yolks together. Gradually add the semolina flour, corn flour and the milk, alternating them until all are incorporated. Place the pan over medium heat and cook this custard, stirring constantly. When the custard thickens, remove from the heat. Beat in the vanilla and the lemon rind then pour the custard over the syrup/pasta base.