• Preheat oven to 180°C (350°F). Grease 23x13 cm (9x5 inch) loaf pan and line with parchment paper. Set aside.
• In a small bowl, whisk together the flour, cornstarch, baking powder and salt.
• Using an electric mixer beat the butter, sugar and orange zest until creamy.
• Add the eggs one at a time, beating well after each addition. Scrape down the sides of the bowl. With a mixer on low speed, add the dry ingredients in 3 additions alternating with the orange juice and sour cream (dry-wet-dry-wet-dry). Do not over mix.
• Pour the batter into the prepared loaf pan and bake for 55-65 minutes, or until a toothpick inserted comes out clean. If using dark colored loaf pan, start checking at 45 minutes.
• Let the cake cool in the pan for 10 minutes, then remove it gently and set it on a cooling rack to cool completely. Once cool, pour the glaze over top. Let the glaze set for 20 minutes, then slice and serve!

Glaze:

• Whisk the powdered sugar and juice together in a large bowl until smooth and pourable. Add more juice if it's to thick or more powdered sugar if it's too runny. Pour it over the cake once cooled.