1. Preheat oven to 175°C (350°F)

2. Grease a 23x33 cm (9x13 inch) baking pan and line with parchment paper

3. In a large bowl, beat butter and granulated sugar together until light and fluffy

4. Add eggs one at a time, mixing thoroughly after each addition

5. In a separate bowl, whisk together flour and baking powder

6. Gradually add the dry ingredients to the butter mixture, mixing until just incorporated

7. Stir in heavy cream, orange zest, and a splash of vanilla extract until the batter is smooth

8. Pour batter into the prepared pan and smooth the top with a spatula

9. Bake for 20 to 25 minutes, or until a toothpick inserted in the center comes out clean

10. Cool the cake completely in the pan on a wire rack

11. Whisk confectioners sugar and orange juice until a smooth, pourable glaze forms

12. Drizzle the glaze over the cooled cake and sprinkle with additional orange zest if desired

13. Cut into squares and serve