For the cake:
3 cups cake flour
1 tablespoon + 1/2 teaspoon baking powder
3/4 teaspoon salt
1 tablespoon ground cardamom
1 cup unsalted butter, softened
2 cups granulated sugar
Zest of one large orange
1 teaspoon vanilla bean paste
4 large eggs
2/3 cup whole milk
2/3 cup buttermilk
1/4 cup fresh orange juice
For the filling:
1/2 cup unsalted butter, softened
1/4 cup cream cheese
3 1/2 cups powdered sugar, sifted
1/2 teaspoon vanilla extract
Zest of half large orange
2 tablespoons fresh orange juice
For the frosting:
6 large egg whites
2 cups granulated sugar
3 cups unsalted butter, softened
1/2 teaspoon vanilla extract
1 teaspoon rose extract (or to taste) or 1 tablespoon rose water (or to taste)
1-2 drops pink food coloring (optional)
To make the cake: Pre-heat oven to 350°F. Grease a 10x15-inch cake pan. Sift together the cake flour, baking powder, salt, and cardamom in a mixing bowl.
In the bowl of an electric mixer, beat the butter on medium-high speed with the paddle attachment until smooth. Add in the sugar, and cream together the butter and sugar until light and fluffy. With the mixer on low, add in the orange zest and vanilla. Add in the eggs, one at a time.
Stop the mixer and scrape down the sides and bottom of the bowl.
With the mixer on low, add in about 1/3 of the flour mixture. Continue to mix while streaming in the milk. Add in another 1/3 of the flour followed by the buttermilk and orange juice. Add in the remaining 1/3 of the flour until just combined. Turn mixer up to medium and mix for no longer than one minute to smooth out batter.
Pour batter into the prepared pan and smooth out with a spatula. Bake until the cake is firm, slightly domed, and a cake tester or toothpick inserted in the middle of the cake comes out clean — about 20 to 22 minutes. Let cool completely on a wire rack before removing cake from the pan. Alternatively, keep cake in the pan until ready to assemble the mini cakes.
To make the filling: In the bowl of an electric mixer fitted with a paddle attachment, beat the butter and cream cheese until smooth. With the mixer on low, carefully add in the remaining ingredients. Once all of the ingredients are added, carefully turn the mixer speed up to medium-high and mix until light and fluffy (about 5 minutes). If filling appears too thick, add in a splash of milk. Mix until smooth.
To make the frosting: In the bowl of an electric mixer, add in the e