Preheat the oven to 350 degrees F.

Grease two 9-inch round baking pans and line the bottoms with parchment paper. Grease the paper.

In a large bowl, combine the white cake mix, the water, the eggs, the canola oil, and 1 tablespoon of the orange zest.

Using a hand mixer, beat the mixture together on low speed for 30 seconds, then on medium speed for 2 minutes.

Stir the cranberries and 1 cup of the walnuts into the batter.

Transfer the batter to the prepared pans.

Bake until a toothpick inserted into the center comes out clean, about 30-35 minutes.

Cool the cakes in the pan for 10 minutes, then transfer the cakes to wire racks to cool completely, making sure to remove the parchment paper.

Allow the cakes to cool completely.

Combine the cornstarch and cranberry juice in a small bowl and whisk well until completely combined. Set aside until needed.

Combine the cranberries, water, sugar, and salt in a medium saucepan. Bring to a simmer over medium heat, stirring occasionally, and cook until the sugar has dissolved about 5 minutes. Continue cooking until the cranberries soften, and some have begun to burst, about 5 more minutes.

Pour in the cornstarch slurry and mix well to combine. Continue cooking, stirring constantly with a wooden spoon or silicone spatula, until the mixture has thickened, about 4 to 5 more minutes.

Remove from heat and stir in the orange juice and vanilla extract.

Scrape into a bowl and cool completely before using.

In the bowl of a stand mixer fitted with the paddle attachment, or in a large bowl using a handheld electric mixer, beat the butter and mascarpone cheese on medium speed, until smooth and creamy, stopping the mixer occasionally to scrape down the sides and bottom of the bowl.

Reduce the mixer speed to low, and gradually add in the confectioners’ sugar, beating each addition well before adding the next. Once all of the sugar has been added, beat in the salt, vanilla, and milk.

Increase the mixer speed to medium-high and beat for 2 to 3 minutes until light and fluffy. If the frosting appears too stiff to spread, add more milk, a teaspoon at a time, until the desired texture is achieved.

Combine 1⁄2 cup of granulated sugar and water in a medium saucepan. Bring the mixture to a rolling boil over medium-high heat and cook, stirring frequently, until the sugar has completely dissolved.

Add in the cranberries and bring the mixture back to a boil, then reduce the heat to a simmer and cook for 1 minute. Remove the cranberries and transfer them to a wire cooling rack using a slotted spoon.

Add the rosemary to the sugar syrup and cook for 1 minute, then use a slotted spoon to transfer to the wire cooling rack.

Allow cranberries and rosemary to sit at room temperature for 10 minutes, or until still slightly tacky to the touch.

Add the remaining granulated sugar to a wide, shallow bowl. Add a few cranberries at a time, and roll them in the sugar until they’re completely coated on all sides. Transfer the cranberries back to the wire rack. Repeat with all the cranberries and rosemary sprigs.

Leave to dry at room temperature for 2 hours before using.

Using a long serrated knife, carefully trim the raised top of each cake, making each one an even, level surface. This will only be a thin layer, as the cakes don’t rise too much in the oven.

Carefully transfer 1 layer to a large plate or cake stand. Spread an even layer of frosting on top, aiming for it to be 1⁄4” in thickness, then top with half of the cranberry filling. Top with another cake layer, and repeat, adding the same ratio of frosting and cranberry filling.

Top with the final cake layer, then use the remaining frosting to cover the top and sides of the cake. Aim for a 1⁄4” thickness of frosting on top, then spread whatever is left around the edges. This is a semi-naked cake, so don’t be alarmed if the sides aren’t totally covered with frosting.

Decorate the cake with sugared cranberries and rosemary. Allow cake to set at room temperature for at least 1 hour before slicing and serving.