Preheat the oven to 325°F (163°C). Line an 8-inch square baking pan with parchment paper, leaving some overhang for easy removal.
Combine the graham cracker crumbs, melted butter, and one tablespoon of sweetener in a bowl. Press firmly into the bottom of the prepared pan.
Bake the crust for 8 minutes. Remove and allow it to cool.
Wash, dry, and finely dice the strawberries. Mash half a banana with the lemon juice.
Beat the softened cream cheese until smooth. Add the sweetener and mix until combined.
Add Greek yogurt, mashed banana, vanilla extract, and salt. Mix on low speed.
Add eggs one at a time, mixing briefly after each addition. Add flour and mix just until incorporated.
Gently fold in the diced strawberries using a spatula.
Spread the filling evenly over the cooled crust.
Bake for 30–38 minutes, until the edges are set and the center has a slight jiggle.
Remove from the oven and cool for approximately one hour.
Cover and refrigerate for at least 4–6 hours, preferably overnight.
Lift the cheesecake from the pan using the parchment paper. Cut into 12 equal bars using a sharp knife.
Add the optional strawberry topping just before serving.