In a medium saucepan combine peanut butter and butter. Heat on medium heat until the butter begins to melt
Once the butter begins melting gently stir it together with the peanut butter until it is combined
Cook the peanut butter/butter mixture for 3-5 minutes or until it just starts to bubble.
While it's cooking add the powdered Swerve to a large mixing bowl. Whisk it thoroughly to blend out any lumps. Set aside Grease an 8x8 inch baking dish on the bottom and sides and set aside
Check on the butter/peanut butter mixture. Once it has come to a low bubble Turn the heat off and add the salt and vanilla.
Carefully pour the peanut butter mixture over the powdered sugar in the prepared bowl. Use a spatula or large wooden spoon and mix it together until it is smooth
Spread the mixture into the prepared baking dish and use a spatula to spread it evenly across the entire dish.
Cover lightly with plastic wrap and place in the refrigerator for 1-3 hours or until firm. Bring to room temperature and cut into desired size squares. Refrigerate leftovers in an airtight container.