Combine 2 cups of fresh cranberries with 1 cup of water in a saucepan. Boil over medium heat, then simmer for 10 minutes until cranberries burst. Strain, stir in ¾ cup of granulated sugar and 1 tablespoon of orange zest, and cool.

Blend 3 segmented oranges until smooth. Mix with the cooled cranberry juice to create a soak for the ladyfingers.

Whisk 1 cup of heavy cream to stiff peaks. In a separate bowl, combine 16 ounces of mascarpone cheese with ½ cup of granulated sugar and 1 teaspoon of vanilla extract. Fold whipped cream into mascarpone, then add ¼ cup of cranberry juice.

Dip ladyfingers quickly in the orange-cranberry soak and layer half in a 9x13-inch dish. Spread half the mascarpone filling over them.

Repeat with remaining ladyfingers and mascarpone filling. Cover with plastic wrap and refrigerate for at least 6 hours, preferably overnight.

Make the cranberry sauce by combining 1 cup of cranberries, ½ cup of water, and ½ cup of sugar in a saucepan. Boil, then simmer for 10-15 minutes until thickened. Cool before blending if desired.

Pour the cranberry sauce over the chilled tiramisu and garnish with sugared cranberries, rosemary, and orange slices. Serve immediately or refrigerate until ready.