Preheat your oven to 350°F. Line the bottoms and sides of two 8-inch round cake pans with parchment paper. Set aside.

In a medium bowl, whisk together the flour, baking powder, and salt. Set aside.

In a large bowl, using a stand mixer or handheld mixer with the paddle attachment, beat the butter, oil, and sugar on medium speed until creamy, about 2 to 3 minutes.

Add the eggs one at a time, mixing well after each addition. Stir in the vanilla and orange zest.

Alternate adding the dry ingredients, milk, and orange juice, starting and ending with the dry ingredients. Mix just until combined—do not overmix.

Divide the batter evenly between the prepared pans. Bake for 28 to 32 minutes, or until a toothpick inserted in the center comes out clean. Let cool in the pans for 10 minutes, then turn out onto a wire rack to cool completely.

In a large saucepan, combine the cranberries, water, orange juice, cornstarch, sugar, and cinnamon. Bring to a boil over medium heat, stirring constantly.

Cook for 3 to 5 minutes until the cranberries soften. Use an immersion blender or potato masher to break them down to your desired consistency.

Continue cooking for another 5 to 6 minutes, stirring frequently, until the mixture thickens and reduces by about one-third. Remove from heat and let cool completely—the filling will thicken further as it cools.

In a large bowl, beat the butter on medium-high speed until soft and creamy, about 1 to 2 minutes.

Add the sifted powdered sugar and beat on medium-low until smooth and fully combined.

Pour in the cooled melted white chocolate and mix on medium speed until creamy. Add 1 to 2 tablespoons of orange juice to reach a spreadable consistency. Taste and add a pinch of salt if desired.

Trim a thin layer off the tops of both cakes to create flat surfaces. Then slice each cake horizontally into two even layers, so you have four layers total.

Place one cake layer on a serving plate. Spread about one-quarter of the frosting over it, building a slight rim around the edge to hold the filling. Spoon one-third of the cranberry filling into the center.

Repeat with two more layers: cake, frosting (with rim), and cranberry filling. Top with the final cake layer.

Frost the outside and sides of the entire cake with the remaining frosting. Refrigerate for at least 4 hours before slicing. Store leftovers in an airtight container in the fridge for up to 3 days.