Lightly coat bunt cake pan with butter and flour. I like to use my butter wrappers for this job, it's a little less messy. Just unwrap your butter, set it in the mixer bowl for later, and rub down the bundt pan. Add a couple tablespoons of pastry flour and shake the pan around to coat it completely.
Set oven to 350℉.
To the bowl of your kitchen aid stand mixer, add room temperature butter, sugar, vanilla extract and salt. Set to speed 2 and mix for 2 minutes.
Increase mixer speed to setting 8 and continue to mix until ingredients are light and fluffy, about 2 minutes.
Reduce mixer speed to setting 4 and begin adding room temperature eggs. Add eggs one at a time, mixing for 30 seconds between each addition.
When the last egg is fully incorporated, pause the mixer and scrape down the sides of the bowl using a rubber spatula.
Add sour cream, ground turmeric, ground ginger, citrus zest. Set mixer to setting 4 and mix for 2 minutes.
In a separate mixing bowl, whisk together the flour, corn starch and baking powder.
Set mixer to setting 2. Add 1/3 of the dry ingredients mixture to the wet ingredients in your stand mixer and mix for 30 seconds.
Pause the mixer, add lemon juice and another 1/3 of dry ingredients. Scrape down sides, set mixer to setting 2 and mix for 30 seconds.
Pause the mixer, add the remaining dry ingredients, scrape down sides with rubber spatula, set mixer to setting 2 and mix for 30 seconds.
Quickly peel and small dice granny smith apples, and toss them lightly with a few tablespoons of pastry flour. Gently fold apples into the cake batter.
Using a rubber spatula, pour the cake batter into the bundt cake pan. Turn the pan and guide with your rubber spatula to get even distribution.
Place the cake in the oven, center rack and bake for 1 hour and 18 minutes.
Remove cake from the oven and allow to cool in the pan for 15 minutes.
Be brave here, flip the cake out onto a cooling rack and allow to cool completely.
Meanwhile, in a clean mixer bowl with whisk attachment, add all icing ingredients at once.
Mix on lowest setting until completely incorporated. Place in the refrigerator until use.
Remove icing from refrigerator 20 minutes before icing your cake. You can whisk it a little more to loosen it up a little.
Pace a cookie sheet under the cooling rack where the cake is resting.
Using a rubber spatula, gently guide and pour the icing over the cake. For even distribution, I pour the icing around the most center point of the cake and use the spatula to help it drape down the sides.
Allow icing to set for 30 minutes.
Carefully transfer the cake to a pedestal or cake plate, garnish with powdered sugar, mint sprigs and edible flowers.
Serve this cake sliced with Chantilly cream and fresh blackberries.