Prep the pan: Line an 8x8-inch baking pan with parchment, leaving overhang on two sides for easy lifting. Lightly mist with nonstick spray.
Make the base: In a bowl, mix almond flour, protein powder, granulated sweetener, and salt. Stir in melted coconut oil and vanilla until the mixture resembles damp sand and holds together when pressed.
Press the crust: Firmly press the base into the lined pan in an even layer.
Use the bottom of a measuring cup to compact it well. Chill while you make the filling.
Strawberry swirl: In a small saucepan, add chopped strawberries, sweetener (if using), chia or cornstarch, and lemon juice. Cook over medium heat for 4–6 minutes, stirring, until juicy and slightly thickened.
Mash lightly. Cool to room temperature.
Cheesecake filling: In a mixing bowl, beat softened cream cheese until smooth. Add Greek yogurt, protein powder, powdered sweetener, lemon zest, lemon juice, vanilla, and salt.
Beat until creamy with no lumps. Taste and adjust sweetness or lemon.
Assemble: Spread the cheesecake filling over the chilled crust. Dollop spoonfuls of the strawberry mixture on top, then use a knife to gently swirl.
Don’t overmix.
Chill to set: Cover and refrigerate for at least 3 hours, preferably overnight, until firm enough to slice.
Slice and serve: Lift the slab out by the parchment, place on a board, and cut into 8–12 bars. Garnish with fresh strawberry slices if desired.
Store: Keep bars in an airtight container in the fridge for up to 5 days or freeze for up to 2 months.