Preheat oven to 325˚F (165˚C). Grease a 12-cup bundt cake pan with melted butter or vegetable oil. Lightly cover with flour. Shake off excess flour.
In a large bowl, whisk together flour, baking powder, baking soda and salt.
In a medium bowl, combine sugar and all the zest. Mix lightly.
In a large mixing bowl with an electric mixer fitted with a paddle attachment, beat the butter until smooth. Add sugar and beat on medium speed for 3 minutes. Scrape down the sides of the bowl. Add cream cheese and beat again for 2 minutes until fluffy. Beat in eggs, one at a time, scraping down the side of bowl as needed. Add vanilla and beat to combine. Mix in flour mixture in two additions until just combined.
Transfer batter to prepared bundt cake and smooth the top. Bake until a toothpick inserted into the cake comes out clean, about 50 – 60 minutes. Cover the cake loosely with a piece of aluminum foil if the top browning quickly. When cake is done, remove from oven and allow to cool for 10 minutes inside the pan.
Invert the bundt cake onto a wire rack set over a large plate or serving dish. If needed, loosen the sides with a thin spatula. Allow cake to cool completely.
For the frosting, in a large mixing bowl with an electric mixer fitted with a paddle attachment, beat cream cheese and butter until smooth. Add blood orange juice, lemon juice and salt. Mix again. Add powdered sugar and beat over high speed until smooth with no lumps. The frosting should be thick. If it’s too thin, add more powdered sugar.
To assemble, place the cake on a cake stand or large plate. Spoon the frosting over the top of the cake. Gently smooth the top with a spatula to allow the frosting flow over the sides. Transfer to the fridge and chill for 30 minutes for the frosting to set. Remove from the fridge and decorate with citrus slices if using. Let the cake comes down to room temperature before serving.