1. Preheat your oven to 175°C and line an 20cm by 20cm baking pan with parchment paper.

2. In a medium-sized bowl, whisk together the almond flour, cocoa powder, erythritol, salt, and baking powder until well combined.

3. In a separate bowl, whisk together the melted butter, eggs, and vanilla extract until smooth.

4. Pour the wet ingredients into the dry ingredients and stir until a thick batter forms. If desired, fold in chopped walnuts or sugar-free chocolate chips.

5. Transfer the batter into the prepared baking pan and spread it evenly.

6. Bake in the preheated oven for about 20-25 minutes or until a toothpick inserted into the center comes out with a few moist crumbs.

7. Remove from the oven and let the brownies cool completely in the pan before cutting into squares.

8. Serve and enjoy your delicious keto brownies!