Preheat oven to 350˚F. Grease 3 8" straight edge cake pans. Line with parchment paper and grease.

In a medium bowl, sift together flour, baking soda, baking powder, and salt. Whisk until completely mixed.

In a standing mixer or with a hand held mixer, cream butter, sugar, and orange zest until light and fluffy, about 5 minutes.

Whisk in eggs, egg whites, vanilla extract, and orange extract on a high speed until combined, about 2 minutes, scraping down sides as needed.

On a low speed, whisk the flour mixture to the egg mixture until just combined.

Still on a low speed, pour in the buttermilk and orange juice, mixing until just combined.

Pour batter evenly into greased layer pans. Bake for 25-30 minutes, until a toothpick comes out clean when inserted into the center of each cake. Set on a wire rack to cool, at least one hour, or frosting will melt.

In a standing mixer or with a handheld mixer, whisk butter and cream cheese until light and creamy.

Sift in 3 cups of powdered sugar.

Add orange zest, orange extract, vanilla paste, and heavy cream. Whisk until completely smooth and fluffy. If too thin, add more powdered sugar. If too thick, add more heavy cream.

When the cake layers are cooled, place one of the cake layers with the flat side down on a plate or cake stand. With an offset spatula, spread the top with about 1 cup of frosting.

Place the second layer on top of this frosted layer and spread another 1 cup of frosting.

Add on the final layer, flat side up to make the cake even. Lightly frost the rest of the cake with the remaining frosting. Place cake in fridge and chill for 10 minutes.

Remove cake from the fridge. Garnish with orange slices, sage leaves, orange and white sanding sugar.

Place in the refrigerator to chill for 30 minutes to an hour, until frosting is set.

Cover cake tightly and store in the fridge for 4-5 days.