Prep the pan and oven: Preheat oven to 325°F (165°C). Lightly grease an 8- or 9-inch springform pan and line the bottom with parchment for easy release.
Make the crust: In a bowl, mix graham crumbs, almond flour, sweetener, melted light butter, and a pinch of salt until it resembles damp sand.
Press firmly into the bottom of the pan using the bottom of a glass.
Par-bake the crust: Bake for 8–10 minutes until set and lightly golden. Let it cool while you make the filling.
Beat the cream cheese: In a large bowl, beat reduced-fat cream cheese on medium speed until completely smooth and fluffy, about 2 minutes. Scrape the bowl well.
Add sweetener and flavor: Mix in the granulated sweetener, vanilla, lemon zest, lemon juice, and salt.
Beat until smooth, then add Greek yogurt and mix just until combined.
Incorporate eggs and starch: Add eggs one at a time on low speed, mixing just until blended. Sprinkle in cornstarch and mix on low until no streaks remain. Avoid overmixing to reduce air bubbles.
Fill the pan: Pour filling over the cooled crust.
Tap the pan gently on the counter a few times to release air bubbles.
Optional water bath: For an extra-smooth top, wrap the outside of the springform with foil and place it in a larger pan. Pour hot water into the outer pan to come halfway up the sides.
Bake: Bake at 325°F for 35–45 minutes, until the edges are set and the center has a slight jiggle. The top should not brown deeply.
Cool gradually: Turn off the oven, crack the door, and let the cheesecake sit inside for 30 minutes.
Then remove and cool to room temperature.
Chill: Cover and refrigerate for at least 4 hours, preferably overnight, to fully set and develop flavor.
Make the berry topping: In a small saucepan, add 1 cup berries, water, sweetener, and lemon juice. Cook over medium heat for 4–6 minutes, stirring, until berries break down. If you prefer a thicker sauce, stir in the cornstarch slurry and simmer 1–2 more minutes.
Off heat, fold in the remaining 1 cup fresh berries. Cool completely.
Assemble and serve: Run a thin knife around the cheesecake edges, release the springform, and spoon the berry topping over the top. Slice with a warm, dry knife for clean edges.