Squeeze one whole lemon and add a tablespoon of baking soda until you make a thick creamy paste. Leave on for up to 20 min, then rinse with cold water. Make sure you make a thick creamy paste. If it's too watery, add more baking soda.
3 Ingredient Nutella Brownies - Bake at for around 30 minutes (less time for cupcake form, more time if the centers aren't baked through). Good for school bake sales - taste more like chocolate cake than brownie though