Boil o.j. and sugar in a saucepan, stirring occasionally, until reduced by half. Add orange zest and set aside to cool.
Meanwhile, whisk chilled cream in a chilled metal bowl until just before the soft peak stage. Add vanilla and cooled orange syrup; continue whipping until soft peaks form.
Sift flour, sugar and baking powder together in a medium bowl. Cut in butter until the mixture resembles coarse crumbs. Combine egg and milk in separate bowl; add to dry ingredients. Stir just enough to moisten - careful not to over mix.
Place batter in a square greased pan and bake at 450 for 15-18 minutes. Use a toothpick to test doneness; should come out clean. Cool in pan 10 minutes before cutting into squares.
Additional Tips
The fresh, sweet-but-not-too-sweet flavors here were lovely with a light late harvest Moscato. We even enjoyed drizzling a bit of the wine directly onto the sponge cake! Try: Eos 'Tears of Dew' Moscato $25.99.