Preheat oven to 350ºF and prepare a large muffin tin with paper liners or parchment paper.
Mix the flour, baking powder, and salt together in a small bowl and set aside.
Cream the butter and sugar together in a large bowl until light and fluffy.
Add the eggs one at a time and mix until fully incorporated, then add vanilla extract and apple butter and mix together.
Mix in half the dry ingredients, then add the milk and stir fully. Fold in the remaining dry ingredients until just combined.
Divide the batter evenly between the muffin tins, using a cookie scoop for consistency.
In a separate bowl, combine the flour, butter, light brown sugar, and cinnamon to make the streusel topping. Sprinkle it evenly over the muffins.
Bake for 35 minutes or until the tops are golden brown and a toothpick comes out clean. Let cool slightly before eating.