For syrup, combine sugar, herbs, rind and 500ml (2 cups) water in a saucepan over medium-high heat. Bring to the boil, stirring to dissolve sugar, then simmer until slightly reduced (6-8 minutes). Remove from heat; stir in juice. Set aside to infuse.
Place milk and spices in a large saucepan; bring to a simmer over medium-high heat. Remove from heat; set aside to infuse (at least 30 minutes; preferably 2 hours).
Whisk eggs and sugar in a bowl until pale and creamy. Add semolina and whisk to combine. Bring infused milk mixture to a simmer; strain over egg mixture (discard solids). Return to pan, whisking continuously over medium heat until thickened (4-5 minutes). Remove from heat; whisk in butter. Pour custard into a bowl and cover with plastic wrap. Set aside to cool.
Preheat oven to 200°C. Grease and line a 20cm x 30cm slice tin with baking paper. Working with one filo sheet at a time (cover remaining filo with a damp tea towel while you work), place filo on a work surface and bush with melted butter; top with another sheet of filo. Repeat with melted butter and 10 more filo sheets to create a stack of 12 layers.
Place stack in lined tin to line base and sides, trimming to fit. Spread custard evenly over filo. Scrunch remaining 12 filo sheets; arrange over custard to cover. Brush generously with remaining butter. Bake until pastry is light golden. Reduce oven to 160°C; bake until golden and starting to puff (30-35 minutes). Pour over half the syrup; cool to room temperature. Slice and serve with remaining syrup.