Prepare Your Oven & Pan: Preheat your oven to 350°F (175°C). Line a 9x9 inch baking dish with parchment paper, allowing some overhang for easy lifting later.
Make the Simple Crust: In a food processor, combine the almond flour, melted butter, 1/3 cup sweetener, 1 egg, and 1 teaspoon vanilla extract. Pulse until a soft, uniform dough forms.
Press the Crust: Firmly press this dough evenly into the bottom of your prepared baking dish. Bake for 10 minutes while you prepare the delicious cheesecake filling.
Whip the Creamy Filling: In a large mixing bowl, use a hand mixer to beat the softened cream cheese and sour cream until the mixture is completely smooth and creamy.
Add Remaining Filling Ingredients: Mix in the 2 eggs one at a time, then add the 1/2 cup sweetener, lemon zest, and 2 teaspoons vanilla extract. Mix until just combined – be careful not to overmix!
Puree the Blackberries: Place the fresh blackberries into a food processor and blend until you have a smooth puree.
Swirl in Berry Goodness: Pour the blackberry puree into the bowl with the cheesecake filling and gently mix until the vibrant berry swirl is beautifully incorporated.
Bake to Perfection: Carefully pour the blackberry cheesecake mixture over the slightly cooled crust in the baking dish and spread it out evenly. Bake for 30-40 minutes, or until the edges are set but the center still has a slight, delicate jiggle.
Chill for Clean Slices: Let the bars cool completely at room temperature, then transfer them to the refrigerator to chill for at least 1-2 hours (or ideally longer) until fully firm before cutting into neat, healthy bars. Enjoy!