1. Prepare the orange curd by whisking together the orange juice, lemon juice, sugar, whole eggs, and egg yolks in a saucepan. Cook over medium-low heat, whisking constantly, until thick enough to coat the whisk. Remove from the heat, stir in the butter and orange zest, strain if desired, and refrigerate until completely chilled.

2. Preheat the oven to 350°F. Grease two 8-inch round cake pans and line the bottoms with parchment paper.

3. Combine the cake mix, eggs, vegetable oil, orange juice, and orange zest until the batter is smooth. Divide evenly between the prepared pans.

4. Bake for 28–32 minutes or until a toothpick inserted into the center comes out clean. Let the cakes cool in the pans for 10 minutes before transferring them to a wire rack to cool completely.

5. Beat the softened cream cheese and butter until smooth. Gradually mix in the powdered sugar, then blend in the orange juice and orange zest until light and fluffy.

6. Trim the tops of the cooled cake layers if needed. Pipe a ring of buttercream around the edge of the first layer, spoon the chilled orange curd into the center, then place the second cake layer on top.

7. Spread on a thin crumb coat and chill for about 20 minutes. Finish frosting the cake with the remaining buttercream and decorate with candied orange slices and fresh orange zest before serving.