Mix the water, sugar, lemon juice and zest with rose water and let them boil. Then remove the syrup and let it cool.
Heat the butter and fry until the semolina turns golden. Gently, while stirring, add the warm syrup. Stir on low heat until the semolina thickens and flavor it with the essence.
Distribute the semolina halva in a lightly greased tray and let it cool well. Serve lemon semolina halva cut into pieces.