01 -
Place blackberries in a food processor and blend until completely pureed, scraping down sides as needed. Pass the puree through a fine-mesh sieve into a bowl to extract the liquid, pressing with a rubber spatula. Discard seeds and solids. Stir in granulated sugar and set aside.
02 -
Preheat oven to 175°C. Grease a 23-centimetre springform pan. Combine graham cracker crumbs, melted butter, granulated sugar, cinnamon (if using), and salt in a bowl. Stir until evenly moistened. Press mixture firmly into the base and 2.5 centimetres up the sides of the prepared pan. Freeze crust while preparing filling.
03 -
In a large mixing bowl, beat cream cheese and granulated sugar with an electric mixer until smooth. Add sour cream, vanilla extract, lemon zest, and salt; mix to combine. Add eggs one at a time on low speed, mixing just until incorporated after each addition. Scrape sides and bottom of bowl and beat for 1 minute to fully blend.
04 -
Pour half of the cheesecake filling into chilled crust. Spoon half the blackberry puree over filling and swirl gently with a butter knife, taking care not to disturb the crust. Repeat with remaining filling and puree.
05 -
Place springform pan on a rimmed baking sheet. Bake in preheated oven for 55 to 65 minutes, or until centre barely wiggles when tapped. Remove from oven and cool to room temperature.
06 -
Cover cheesecake loosely with plastic wrap. Refrigerate overnight, at least 8 hours, to set.
07 -
Chill a mixing bowl and mixer beaters for 20 to 30 minutes. Whip cold heavy cream until it thickens, then add powdered sugar and vanilla extract. Continue beating until stiff peaks form.
08 -
Pipe or spread whipped cream around the perimeter of the cheesecake. Garnish with fresh blackberries. Slice and serve. Store leftovers covered in the refrigerator up to 4 days, or freeze tightly wrapped for up to 1 month.