Preheat the oven to 350°F
Whisk together your dry ingredients first - the semolina, baking powder, baking soda, salt and sugar.
2 cups Semolina, 1 Tablespoon Baking Powder, 1½ teaspoon Baking Soda, ½ teaspoon Salt, ⅔ Cup Brown Sugar
Add the eggs and buttermilk, whisking to combine.
2 Eggs, 1¼ Cups Buttermilk
Finally add the melted butter, grapefruit zest and vanilla whisking until smooth.
¾ Cup Melted Butter, 4 Lemons, 1.5 teaspoon Vanilla
Pour your batter into an 8-inch cake pan that has been greased and lined with parchment paper - bake for 25 minutes, or until your cake passes the toothpick test and allow it to cool completely.