In a large bowl whisk flour, baking powder, baking soda, and salt. Set aside.

In the bowl of a stand mixer fitted with the paddle attachment, beat butter, oil, sugar, and orange zest on medium speed for 2-3 minutes, until light and fluffy. Add eggs one at a time, followed by vanilla extract. Beat until combined, scraping the sides and bottom ofthe bowl as needed.

In a liquid measuring cup combine orange juice and buttermilk.

Add one third of the dry ingredients to the sugar/egg mixture, beat until just combined.

Add half of the buttermilk, beating until just combining. Repeat adding half the remaining flour, all the remaining buttermilk, then the remaomomg flour, beating between each addition.

Stir with a rubber spatula to make sure it is completely combined.

Pour the batter into the pan and smooth into an even layer.

Place the pan on the center rack off the preheated oven and bake for 40-50 minutes, or until a toothpick inserted into the center comes out clean.

Place the pan on a wire rack to cool in the pan for 30 minutes

After 30 minutes of cooling, carefully invert the cake directly onto the cooling rack.

Place a large piece of parchment paper or foil under the rack to catch the syrup that drips through.

Spoon or brush the syrup onto the cake. The cake should still be a bit warm so it will soak up the syrup.

Allow the cake to cool completely before proceeding with the icing.

Add the butter to the bowl of a stand mixer fitted with the paddle and whip until creamy,.

Add the powdered sugar and whip until combined.

Add the heavy cream, orange zest, and vanilla extract, beating until smooth and creamy.

Adjust the consistency of the frosting by adding more powdered sugar to thicken or more heavy cream to thin it out. Drizzle the icing on top of the cooled cake.

Garnish with grated orange zest.