Preheat oven to 325F and grease a 9x9 baking pan well (you can use an 8x8 but the cake will take a little longer to cook).
In a large bowl, whisk together the almond flour, sweetener, whey protein, baking powder, and salt. Stir in melted butter, eggs, vanilla extract and almond milk until well combined.
Spread batter in prepared baking pan and bake 25 to 30 minutes or until edges are beginning to brown and top is firm to the touch. Remove and let cool, then use the handle of a wooden spoon to poke large holes all over the cake.
In a medium saucepan over medium heat, combine strawberries and water. Bring to a boil and then simmer until berries are very soft. Puree in a blender or with a hand blender, then stir in the sweetener.
Sprinkle surface with xanthan gum and whisk vigorously to combine. Let cool until somewhat thickened.
Pour filling over cake and tap the baking pan gently on the counter to help it fill the holes. Refrigerate until set, about 1 hour.
In a medium bowl, combine whipping cream, sweetener, and vanilla extract and beat until stiff peaks form. Spread over cake and refrigerate another hour or so to firm up.