In a small bowl combine the sugar with the zest of the oranges until fragrant.
In a large bowl whisk together the orange sugar, 2 cups of flour, baking powder, baking soda, and salt.
To the same bowl add the buttermilk, orange juice, vanilla, and oil and beat with the paddle attachment of a stand mixer or a hand mixer just until fully combined.
In another bowl whip the egg whites until medium-stiff peaks form. Fold ⅓ of the egg whites into the cake batter to loosen it up, followed by the remaining egg whites. Fold until only a few streaks of egg whites remain.
Toss the cranberries with the remaining ¼ cup of flour. Fold into the cake batter until just combined.
Separate the cake batter evenly into the two cake pans and bake for about 30-35 minutes, until a toothpick comes out clean and the center of the cake springs back when lightly pressed. Let cool completely before frosting. Top with sugared cranberries and enjoy!
White Chocolate Buttercream
In a small bowl melt the white chocolate in the microwave in 30-second intervals. Allow the fully melted chocolate to cool down for at least 10 minutes until it is room temperature, not warm to the touch.
In a large bowl add the softened butter and beat for 2-3 minutes until smooth and light. Reduce the mixer speed to low and slowly add in the cooled white chocolate until fully combined and smooth.
Add in the powdered sugar, vanilla, and salt and mix on low until nearly completely absorbed before increasing the speed to high. Whip for 2-3 minutes until smooth and fluffy. Add the tablespoon of heavy cream and mix on medium speed until smooth and silky.