Getting butter tarts out of the pan is the most stressful part of making them at home. First, when they come out of the oven, let them cool for about 5 minutes to firm up a little. Then you can use your fingertips to gently twist them in the pan to loosen the sides. Once completely cooled, then you can pull them out of the muffin pan one by one using your fingertips. You can also use a pairing knife or an offset spatula to help you lift them out.