Combine the syrup sugar and water in a saucepan. Bring to a boil, reduce heat and simmer for 10 minutes. Add lemon juice during the final minute. Remove from heat and cool completely.
Preheat the oven to 350°F / 180°C. Grease a 9-inch / 23 cm cake pan.
Beat the eggs and sugar for 3 to 4 minutes until pale and airy.
Add the yogurt, oil, lemon zest and optional vanilla. Mix until combined.
In a separate bowl, mix semolina, flour, baking powder and salt.
Fold the dry ingredients into the wet mixture just until combined.
Pour into the prepared pan and bake for 30 to 35 minutes, until golden and cooked through.
Rest the warm cake for 5 minutes, then slice into squares or diamonds.
Slowly pour the completely cooled syrup over the warm cake.
Rest for at least 1 hour, then garnish with pistachios or coconut before serving.