Preheat oven to 350ºF. Butter and flour a 10" bundt pan, making sure to grease all of the nooks and crannies.
In a large bowl, whisk together flour, baking powder, baking soda and salt.
In a stand mixer, beat butter and sugar together until light and fluffy, 3 full minutes, pausing occasionally to scrape down sides of bowl. Beat in eggs, one at a time, and then vanilla extract.
With mixer speed on low, beat in 1/3 of the flour mixture followed by 1/2 of the orange juice. Repeat, ending with the final 1/3 of the flour mixture. Scrape batter into prepared bundt pan and bake for about 60 minutes, until centre feels springy when lightly pressed. Start checking cake around 40 minutes and tent it with foil if it's browning too quickly.
Cool cake in the pan for 10 whole minutes. Cover with a wire cooling rack and flip the pan over so that the cake is on the rack. Tap assertively on the bottom if the cake isn't releasing. (10 minutes in the hot pan are needed for the bottom to steam and facilitate removal.) Allow cake to cool completely on rack before icing.
To make the icing, whisk confectioners' sugar with juice to a smooth consistency. Place cooled cake on serving plate and spoon icing over top, allowing it to fall into centre and down sides. Garnish with edible flowers if desired.