Cake

1. 5 eggs
2. 110 mL (⅓ cup + 2 tbsp.) well packed brown sugar, divided
3. 100 mL (⅓ cup + 4 tsp.) all purpose flour

Spicy orange syrup

1. 125 mL (½ cup) orange juice
2. 80 mL (⅓ cup) sugar
3. ½ vanilla bean, split lengthwise and scraped or 5 mL (1 tsp.) vanilla extract
4. 2 mL (½ tsp.) ground spices (mixture of equal parts cinnamon, cardamom, and star anise)

Brown sugar buttercream

1. 3 eggs
2. 310 mL (1¼ cup) well packed brown sugar
3. 125 mL (½ cup) water
4. 625 mL (2½ cups) unsalted butter, room temperature
5. ½ vanilla bean, split lengthwise and scraped or 5 mL (1 tsp.) vanilla extract
6. 7 mL (1½ tsp.) orange zest (about ½ orange)