Place the juice in a small saucepan; bring to a simmer over medium-high heat. Remove from heat; stir in saffron. Let stand 10 minutes.
Lightly spoon 2 cups flour into dry measuring cups, and level with a knife. Combine flour, baking powder, and salt, stirring well with a whisk. Set aside.
Place sugar, egg, and egg white in a large bowl, and beat with a mixer at medium speed for 5 minutes or until thickened. Add yogurt, beating well. Gradually add oil and juice mixture, beating until well blended. Add half of flour mixture to sugar mixture; beat just until blended. Repeat procedure with the remaining flour mixture.
Spoon batter into a 9-inch round cake pan coated with cooking spray. Bake at 350° for 40 minutes or until a wooden pick inserted in center comes out clean. Cool for 5 minutes in pan on a wire rack; remove from pan. Cool completely on wire rack.
Place cake on a serving platter. Combine marmalade and liqueur in a small saucepan; bring to a simmer over medium heat, stirring constantly. Remove from heat; strain through a fine sieve directly onto surface of cake. Discard solids. Spread marmalade mixture evenly over top of cake, allowing excess to drizzle down sides of cake.