Preheat oven to 325 °F (165 °C) and grease three 8-inch round cake pans. Line bottoms with parchment and grease again.

In a bowl, whisk together almond flour, sweetener, cocoa powder, protein powder, baking powder, and salt.

Stir in sour cream, eggs, and vanilla. Add water, 1 tablespoon at a time, until batter is thick but pourable.

Divide batter among prepared pans and bake for 15–20 min or until just firm. Cool completely.

For frosting, beat peanut butter, cream cheese, and butter until smooth. Add sweetener and vanilla.

Whip heavy cream separately until stiff peaks form, then fold into peanut butter mixture.

Place one cake layer on a serving plate, spread ¼ of frosting, then repeat with remaining layers. Chill for 1 hour to firm up.

For glaze, heat cream to a simmer, remove from heat, add chocolate and let melt.

Whisk in sweetener and allulose, cool slightly, then drizzle over cake, letting it drip down the sides.

Add optional toppings like keto peanut butter cups or sprinkles.