• Place oven racks in the center of the oven. Preheat oven to 350° F.

for the crust-

• Prepare a 9-inch springform pan by spraying with non-stick cooking spray and lining with parchment paper on bottom and sides. Spray the parchment paper with non-stick cooking spray as well, and set aside.
  
• In a food processor, grind graham crackers into fine crumbs. Add granulated sugar and pulse a couple times to combine.
  
• While pulsating food processor, stream in melted butter until all crumbs are moist.
  
• Using the bottom of a cup, press graham cracker crumbs into the bottom and half way up the sides of the springform pan.
  
• Bake 7 minutes. Remove from oven and set aside.
• Reduce oven temperature to 325° F.

for the blackberry puree (for swirling inside cheesecake AND for the blackberry sauce drizzle)-

• Place blackberries, granulated sugar, and lemon zest in a food processor or blender to puree.
  
• In a small saucepan over medium heat, combine the pureed blackberry mixture. Cook while stirring occasionally until the sugar dissolves completely, about 5–7 minutes.
  
• Press blackberry puree through a fine mesh strainer to remove seeds. This should yield about 1 cup of puree. Discard seeds and set HALF of the blackberry puree aside to cool.
  
• Add the other half of the puree back to the small saucepan and place over medium heat. Whisk in the cornstarch and cook for a few minutes until it thickens a bit, stirring occasionally. Set aside.
  

for the cheesecake-

• In a large bowl or bowl of a stand mixer, mix cream cheese 30 seconds until smooth. Scrape the sides and bottom of the bowl and add in granulated sugar, sour cream, and vanilla extract.
  
• Mix again until incorporated. Scrape the sides and bottom of the bowl VERY WELL and mix again briefly.
• Crack eggs into a separate bowl and whisk until well beaten. With the mixer on low, slowly pour the eggs into the cream cheese mixture and stop stirring once eggs have been incorporated.
  
• Remove bowl from mixer and scrape the sides and bottom again, ensuring the entire mixture is smooth. If there are a few small lumps, try to fold in using a rubber scraper.
  
• Once the batter is completely smooth and ready, tap the bowl on the counter for 30-45 seconds to remove as many air bubbles as possible. You should see them popping on the surface as you tap the bowl.
• Pour HALF of the cheesecake filling into the center of the graham cracker crust and gently smooth the top if needed.
  
• Next add half of the blackberry puree, using a spoon to drop small dollops evenly over the surface of the cheesecake mixture. Space them out across the top to ensure the puree is distributed evenly.
  
• Gently drag a butter knife or a skewer through the dollops of blackberry puree in a swirling motion. Be careful not to over mix or run into the graham cracker crust. Aim for a marbled pattern by moving the knife back and forth to create delicate swirls.
  
• Pour the remaining half of the cheesecake mixture overtop the blackberry swirls.
  
• Then, add the rest of the blackberry puree in dollops just like before and create swirls again.
  
• Bake at 325° F for 30 minutes.
• Reduce heat to 250° F and bake for another 30 minutes.
• Once this time has elapsed, turn oven off and keep cheesecake inside for another 30 minutes for some carryover cooking without opening the oven door.
• Crack oven door to let cheesecake cool slowly for 1 hour before removing. At this point, cheesecake should be slightly warm.
• Bring cheesecake to room temperature on the counter (3-4 hours) before covering with plastic wrap and transferring to the fridge.
  
• When ready to serve, open springform pan and remove collar. Cut cheesecake into slices and serve with a healthy drizzle of blackberry sauce.