1. Preheat the oven to 325F. Line an 8-inch round springform pan with parchment, and coat with nonstick spray. Thoroughly cover the outside of the pan with aluminum foil to prevent any water from leaking into it during the baking process.
2. Mix together the graham crackers, brown sugar, flour, salt, and butter. Once everything has been moistened a bit, press the mixture into the pan.
3. Using a stand mixer fitted with a paddle attachment, beat together the cream cheese, 1C of sugar, salt, lemon extract, and lemon zest. Add the egg yolks and beat until smooth.
4. Transfer the cream cheese mixture to a large bowl and thoroughly clean the bowl of your stand mixer.
5. To the (now clean) mixer bowl, beat the egg whites with the remaining 1T sugar until soft peaks form. (You can do this with a handheld mixer instead if you have one.)
6. Very gently fold the egg whites into the cream cheese mixture and pour your filling over the crumb crust.
7. Cover the top of the pan with foil to prevent the top from browning and place it in a large roasting pan.
8. Transfer the roasting pan into the oven and create a water bath by pouring hot water into the roasting pan until it hits about 1-inch up the side of the springform.
9. Start checking your cheesecake after 1 hour and 20 minutes. You will know it’s done when the center is set and no longer jiggles when lightly shaken. (It takes my very old and hard-working oven about an hour and a half.)
10. Remove the cake and chill in the refrigerator for at least 6 hours to ensure it is completely set.

Make the blackberry sauce:

1. Combine the water and cornstarch in a small bowl and set aside.
2. In a small saucepan, cook the blackberries and sugar over medium heat. Break up the blackberries and stir until they are soft and release their juices, about 5min. Stir in the water/cornstarch mixture and lemon juice and bring to a simmer, allowing the mixture to thicken, roughly 10 min.
3. Take off the heat and allow to cool completely before transferring to a saucer and pouring over cheesecake. This holds up really well in the refrigerator, so feel free to make this a day or two ahead.