Preheat your oven to 180°C (350°F).
In a mixing bowl, combine the semolina, all-purpose flour, sugar, baking powder, and coconut flakes.
Add the melted vegan butter, almond milk, and vanilla extract to the dry ingredients. Mix well until a thick batter forms.
Grease a baking dish with vegan butter or oil. Pour the batter into the baking dish and spread it evenly.
Use a knife to score the batter into diamond or square shapes.
Bake in the preheated oven for about 30 minutes or until the top turns golden brown.
While the cake is baking, prepare the syrup. In a small saucepan, combine the sugar, water, and lemon juice. Bring it to a boil and simmer for 10-15 minutes until the syrup thickens slightly. Stir in the rose water (if using) and remove from heat.
Once the cake is done, remove it from the oven and immediately pour the hot syrup over it. Allow the cake to absorb the syrup for about 15 minutes.
Garnish the basbousa with slivered almonds or pistachios and shredded coconut.
Let it cool completely before cutting and serving.