- Preheat oven to 350 degrees. Spray cast iron skillet with cooking spray.
- Melt the butter and add the erythritol to it. Stir until erythritol is dissolved.
- Stir together the cocoa powder, salt, and vanilla. Add the butter to the mixture and stir.
- Add the egg(room temperature) to the batter and mix until incorporated.
- In a separate bowl, stir together the almond flour and the baking powder. Add the flour to the batter and mix in.
- Chop up the walnuts. Fold the walnuts into the batter.(I prefer to add sugar free chocolate chips)
- Pour the batter into the skillet and bake for 30 minutes. Cast iron skillets retain heat so make sure not to over cook the brownies. The top will still be slightly jiggly.
- Melt the butter and peanut butter together in a microwave. Pour over the finished brownies. Let the brownies cool and slice into 4 slices.