To prepare cake, Combine flour, baking powder, baking soda, and salt in a medium bowl; stir with a wisk. Place 1 cup sugar and butter in a bowl; beat with a mixer at high speed for 2 minutes. Add eggs, one at a time, beating well after each addition. Scrape seeds from vanilla bean; add to butter mixture. Add rind, juice, and yogurt to bowl, and mix until smooth. Gradually add to flour mixture; beat on low speed just until combined. Pour batter into a 9x5 inch loaf pan coated with cooking spray. Bake for 65 minutes or until a wooden toothpick inserted in the middle comes out clean. Cool in pan 10 minutes on a wire rack. Take out of pan and place on the wire rack. Pierce top of cake with a fork or wooden skewer.
To prepare syrup, combine water, sugar, and juice in a saucepan. Bring to a boil; cook for 7 minutes. Remove from heat, stir in liqueur and vanilla extract. Brush syrup over sides and top of cake. Cool completely. Serves 12