Line the base of springform or regular circular 9 inch cake pan with parchment paper. Lightly grease the sides with butter and keep aside until ready to use.

Place the butter and sugar in the bowl of a stand mixer and using the paddle attachment cream until light and fluffy on medium high speed for about 5 minutes. Add the tahini and beat for another minute until combined.

Add one egg at a time to the creamed butter and sugar mixture and mix on medium-high speed until completely combined.

Add the vanilla extract and coconut rum (if using). Beat for 30 seconds until completely mixed.

In a large mixing bowl, lightly whisk, the semolina, coconut, salt, baking powder and 1 ½ tablespoons of the black sesame seeds. Pour half of this mixture into the creamed butter-sugar-egg mixture and combine using the paddle attachment. Pour in the rose water and coconut milk. Add the rest of the semolina mixture and combine on medium speed until smooth. Pour the batter into the prepared cake pan and smooth the surface with an offset spatula (wet the spatula with a little cold water, to prevent the batter from sticking). Sprinkle the rest of the sesame seeds on the surface of the cake batter. Cover the cake with cling film and refrigerate for at least 4 hours to overnight before baking.

To bake the cake, place a wire rack in the center of the oven and preheat to 350F. Remove the cling film and bake for 45-50 minutes turning the cake half way through baking. The cake is done with the top is slightly golden and the center is firm to touch or when a knife or skewer when passed through the center of the cake comes out clean from the center. Remove the cake from the oven and allow it to cool for 30 minutes in the cake pan. Run a knife around the edges of the baked cake, remove and allow to cool to room temperature before serving. To store, I recommend refrigerating in an airtight container or freezing the extra (bring to room temperature before serving).