For the white cake:

1. Preheat the oven to 350 degrees F (180 degrees C). Grease and line two 6 inch cake pans with parchment paper.
2. In the bowl of a stand mixer fitted with the paddle attachment, combine the flour, sugar, baking powder, and salt.
3. Cut up the butter into small cubes and add to the dry ingredients. Mix on low speed until it resembles wet sand.
4. Add the oil, yogurt, milk, and vanilla, and mix until fully combined.
5. In a small bowl, beat the egg whites with an electric mixer until medium peaks form.
6. Gently fold the whipped egg whites into the batter until just combined.
7. Divide the batter evenly between the prepared cake pans.
8. Bake for 28-32 minutes or until a toothpick inserted comes out clean.
9. Cool completely before decorating.

For the cranberry jam:

1. Add the cranberries, sugar, orange zest, orange juice, and salt to a medium saucepan.
2. Heat over medium heat for 10-12 minutes stirring often until the cranberries start to break down.
3. Reduce heat to low, and cook for another 8-10 minutes, stirring frequently until it has thickened.
4. Remove from heat and use an immersion blender (or transfer to a blender) and blend until smooth.
5. Pour into a glass jar to cool completely, then chill in the fridge until ready to use.

For the orange curd:

1. In a medium bowl, whisk together the sugar, cornstarch, and salt until no lumps remain.
2. In a medium saucepan over low-medium heat, melt the butter.
3. Whisk in the sugar mixture, then the lemon juice and egg yolks until fully combined, about 1 minute.
4. Use a rubber spatula to constantly stir the mixture for another 2-3 minutes or until large bubbles form in the center. Immediately remove from heat.
5. Strain the lemon curd into a bowl. Press plastic wrap up against the surface to prevent a skin from forming, and chill for at least 2 hours or overnight.

For the mascarpone frosting:

1. In the bowl of a stand mixer fitted with a whisk attachment, combine the mascarpone, heavy cream, and sugar.
2. Whisk on low speed until combined and smooth, then turn up to medium-high speed until thick.

For assembly:

1. Secure the first layer of cake on the cake stand with a small amount of frosting.
2. Transfer some of the frosting to a piping bag, then pipe a dam around the edge of the cake. Spread a thin layer of cranberry jam in the center.
3. Pipe another layer of frosting around the edge, then spread a thin layer of orange curd in the center.
4. Place the second cake layer on top, and over the whole cake in a thin layer of frosting for the crumb coat.
5. Place in the fridge for about 15 minutes, then frost the cake as desired.
6. Decorate the cake with orange slices, cranberries, and rosemary, if desired.