Preheat your oven to 325°F (165°C) and line a 9-inch square baking pan with parchment paper, leaving enough parchment hanging over two sides to lift the finished cheesecake out later.

In a medium mixing bowl, combine the finely ground almond flour, 3 tablespoons granulated keto-friendly sweetener, melted unsalted butter, and ½ teaspoon vanilla extract. Stir until the mixture is evenly moistened and resembles soft, damp crumbs.

Transfer the almond flour mixture to the prepared pan and press it firmly and evenly across the bottom. Use the bottom of a measuring cup or the back of a spoon to create a compact, level crust.

Bake the crust for 8–10 minutes, just until lightly golden and fragrant. Remove it from the oven and allow it to cool for several minutes while you prepare the cheesecake filling.

Place the softened cream cheese in a large mixing bowl and beat on medium-low speed until completely smooth. Scrape down the sides of the bowl so there are no hidden lumps of cream cheese.

Add the sour cream and ½ cup granulated keto-friendly sweetener. Mix gently until the ingredients are fully incorporated and the filling looks smooth and creamy.

Add the eggs one at a time, mixing gently after each addition until just combined. Avoid overmixing because incorporating too much air can cause the cheesecake to puff and crack during baking.

Add 1 teaspoon vanilla extract and 1 tablespoon fresh lemon juice. Mix briefly until incorporated, then scrape the sides and bottom of the bowl one final time.

Gently fold 1 cup of finely diced strawberries into the cheesecake mixture using a rubber spatula. Fold carefully so the berries remain intact and don't release excessive liquid into the filling.

For the optional strawberry swirl, combine ½ cup chopped strawberries, 1 tablespoon keto-friendly sweetener, and 1 teaspoon lemon juice in a small saucepan. Cook over medium-low heat for approximately 4–6 minutes, stirring occasionally, until the berries soften and become juicy. Allow the mixture to cool slightly.

Pour the cheesecake filling over the partially cooled almond flour crust and spread it gently into an even layer with a rubber spatula.

Spoon small amounts of the strawberry mixture over the cheesecake surface if using the optional swirl. Drag a toothpick or thin knife gently through the strawberry mixture to create a simple marbled pattern.

Bake the cheesecake at 325°F (165°C) for approximately 35–45 minutes, or until the edges are set and the center still has a slight gentle jiggle when the pan is moved.

Remove the cheesecake from the oven and allow it to cool completely at room temperature. Do not slice it while warm because the filling will still be soft.

Once cooled, cover the pan and refrigerate the cheesecake for at least 4 hours, preferably overnight, so the filling can fully firm up and develop its best texture.

Use the parchment-paper overhang to lift the chilled cheesecake from the pan and place it on a cutting board. Use a sharp knife to cut it into 16 bars, wiping and drying the knife between cuts for cleaner slices.

Serve the cheesecake bars cold, optionally topped with a few fresh strawberry slices, a small spoonful of keto-friendly whipped cream, or a little lemon zest.