Preheat your oven to 190°C (375°F). Lightly coat the base and sides of a 9x13-inch baking dish with tahina to prevent sticking and add subtle nutty undertones.
In a large mixing bowl, combine the ghee, condensed milk, and baking powder. Stir in the semolina, desiccated coconut, and water, mixing until you achieve a thick, cohesive batter.
Transfer the mixture into the prepared baking dish and use a spatula or the back of a spoon to spread it out evenly, smoothing the surface.
Place the dish in the preheated oven and bake for 33 to 35 minutes, or until the top turns a deep golden brown and the edges begin to pull away slightly from the sides.
While the cake bakes, prepare the syrup. Combine the sugar and water in a heavy-bottomed saucepan and bring to a boil. Once boiling, reduce the heat and simmer gently for 6 to 8 minutes.
Remove the syrup from the heat and stir in the lemon juice and rose water or orange blossom water. Set aside to cool to room temperature.
As soon as the basbousa is out of the oven, slowly ladle the syrup over the hot cake, distributing it evenly. Pour gradually, section by section, using a tablespoon to ensure the syrup soaks in evenly—avoid pouring it all in one spot.
Allow the cake to absorb the syrup fully. For best results, let it rest for 45 minutes to an hour before slicing.
Cut into neat squares or diamonds, garnish with a dusting of desiccated coconut, and serve with fresh berries or a sprig of mint if desired.