Directions

• Preheat the oven to 350°F. Grease a 9-inch cake pan generously with the butter, being especially generous when coating the base of the pan.
• Sprinkle the brown sugar evenly over the base of the pan. Arrange the citrus in lines across the cake pan, starting with lemon slices on the left side. Follow with lines of navel orange slices, then cara cara slices and finally blood orange slices to create an ombré effect. Overlap the pieces slightly to fit in as many as possible.
• In the bowl of an electric mixer fitted with the paddle attachment, cream the butter, granulated sugar and light brown sugar until light and fluffy, about 4 minutes.
• Add the eggs one at a time, mixing well to combine. Add the vanilla extract and mix to combine.
• Add the all-purpose flour, whole-wheat flour, cinnamon, baking powder, baking soda and salt. Mix to combine.
• Add the sour cream and mix well to combine. Pour the batter over the prepared citrus slices and gently spread into an even layer.
• Bake until a toothpick inserted into the center of the cake comes out clean, 40 to 45 minutes. Let cool for 10 minutes inside the pan before inverting onto a cooling rack to cool completely.