Gather all ingredients and have them ready for use.
Place cottage cheese, protein powder, cocoa, sugar substitute, baking powder, salt, and 1 ounce of milk in a blender or food processor.
Blend the mixture until smooth, adding more milk if it is too thick, aiming for a thick but not soupy consistency.
Optionally, lightly spray a microwave-safe bowl with cooking spray for easier removal later.
Pour the blended batter into the prepared bowl.
Microwave on high for 1 to 2 minutes, monitoring to avoid overcooking and dryness.
Alternatively, bake at 350°F (176°C) for 15 to 20 minutes if preferred.
Allow the brownie to cool slightly before serving to enhance flavor and make handling easier.