Powder The Mastic. Take 2 tablespoons out of the 270 grams of sugar and place it in a small food processor together with the Mastic tears. Blend until Mastic turns into powder. Alternatively, you may use a pestle to powder the Mastic again together with the 2 tablespoons of sugar.
In a mixing bowl whisk together the Greek yogurt, water, and sugar until smooth.
Add the lemon zest, vanilla, baking soda, and ground Mastic. Stir well to combine. The baking soda will turn the mixture foamy.
Gradually mix in the semolina. Whisk until fully combined and thickened.
Mix in the melted butter as well.
Cover and rest at room temperature for 2 hours. For the semolina to get nice and fluffy.
Preheat the oven to 175°C / 350°F.
Grease a 12-inch (31 cm) round baking pan with 1 teaspoon of butter.
Transfer the cake mixture to the pan. Spread it evenly. Then with a tablespoon dipping it in cold water smoothen the top a bit.
Bake the semolina cake for 20 minutes on the lowest rack of your oven. Then take the pan out of the oven and cut the cake into rhombus-shaped or square pieces. At this point start to make the syrup (see below).
Place the pan back in the oven and bake for about 20-25 minutes more. The surface of the cake should get a warm honey brown color.
For The Syrup:
Add all of the ingredients for the syrup to a small cooking pot. Without stirring bring to a boil over high heat.
Cook the syrup for 6-7 minutes from the time it starts to boil and bubble. It will thicken slightly but not too much.
Ladle the hot syrup all over the hot cake. Let the cake cool down inside the oven for a couple of hours with the door of the oven open. This will make the cake cool down slowly giving it time to absorb all of the syrup. (see Note 1 below)
Once the cake gets to room temperature place it in the fridge. Refrigerate, ideally overnight.
Serve on its own or with whipped cream or a scoop of vanilla ice cream.
Video
Notes
Note 1: The syrup should be added to the cake right as the cake comes out of the oven. As they both need to be hot.