Preheat the oven to 325ºF and grease a 9 to 10 cup capacity bundt pan well.
In a medium bowl, combine the chopped nuts and sweetener. Add the melted butter and stir until well combined.
Sprinkle evenly in the prepared bundt pan.
In a large bowl, whisk together sour cream, eggs, and vanilla extract until smooth.
Add the almond flour, sweetener, protein powder, coconut flour, baking powder, cinnamon, and salt and stir until well combined. Stir in just enough water until a spreadable consistency is achieved.
Spread the batter over the topping in the pan. Bake 45 to 55 minutes, or until the top is golden brown and just firm to the touch.
Remove and let cool 20 minutes in the pan, then gently loosen and flip out onto a cake platter.
In a small saucepan over medium heat, combine the allulose honey and water. Bring to a simmer and cook 3 minutes to thicken slightly.
Remove from heat and stir in the powdered sweetener and the lemon juice. Drizzle over the cooled cake. You can reserve some for serving with individual slices too.
