Preheat oven to 350 °F.
Mix flour, semolina, coconut powder, salt, baking powder, and set aside.
In another bowl combine the sugar and the orange zest. Massage the zest with the sugar using your fingers for 1 minute to release the oils in the zest.
Add the eggs, milk, orange juice, oil, orange blossom water, melted butter, and yogurt.
Whisk together well until no longer lumpy.
Add the wet ingredients on top of the dry mixture and fold until combined.
Add the tahini to your 9×13 tray and brush it evenly, making sure to get to the corners.
Pour the basbousa batter and smooth the top.
Bake at 350 °F for 25-35 minutes or until a toothpick comes out clean.
Once out the oven, immediately pour simple syrup on top(I used the whole amount of syrup). Make sure the syrup is warm.
Let it cool completely at room temperature, about 2-3 hours, covered so it doesn't dry out.
When it's time to cut, use a sharp knife, and wipe the knife after each cut in order not to ruin the shape. Make sure to cut carefully.