Spray mini muffin tins with cooking spray. Preheat oven to 375 degrees.
Use a 2 inch cookie cutter to cut circles of pie dough, or tear off pieces of pie dough and press into the bottom and up the sides of each muffin cup. Place about 1/2 a teaspoon of apple butter into each cup. The cup should be full.
In a small bowl, mix the flour, cinnamon, brown sugar and oats together. Cut in the butter and mix until crumbly. Sprinkle the streusel over the top of each of the tarts.
Bake at 375 for 18-20 minutes or until the crust is lightly browned. Allow the tarts to cool for 10 minutes, then remove from the pan to a wire rack to cool completely.
Store in an airtight container.
Notes
If you like nuts, substitute chopped walnuts for the oatmeal in the streusel. You can mix 1/2 cup powdered sugar and 1-2 tablespoons of milk until smooth, then drizzle it over the top of each tart for a glaze if desired.