In a medium saucepan over medium heat, combine the cherries, raspberries, and water. Bring to a boil, then reduce the heat to a simmer and cook until the berries can be easily mashed with a fork, about 4 minutes.
Remove from heat and stir in the powdered sweetener and the cherry extract. Set aside.
Preheat the oven to 325F and grease a 15 by 10 inch jelly roll pan. Line the bottom of the pan with parchment and grease the parchment.
In a large bowl, whisk together the almond flour, sweetener, cocoa powder, coconut flour, protein powder, baking powder, and salt. Stir in the eggs, butter, and vanilla extract until well combined.
Stir in 1/2 cup water until well combined. If the batter is overly thick, stir in more water 1 tbsp at a time. The batter should be spreadable but not quite pourable.
Spread the batter evenly in the prepared pan, and smooth the top with an offset spatula. Bake 15 to 20 minutes, until the top is firm to the touch. Remove and let cool completely in the pan.
Once cool, spread the cherry filling evenly over the top of the cake, spreading out the cherry bits as evenly as possible.
Whipped Cream Frosting
In a large bowl, combine the cream, sweetener, cherry extract and vanilla extract. Beat until the cream holds stiff peaks.
Spread about 3/4 of the whipped cream over the cake, as evenly as possible. Use the remaining cream to pipe rosettes decoratively on the top of the cake.