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

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.

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.

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.