Apple Cinnamon Blueberry Muffins

1 1/2 cups all-purpose flour

3/4 cup white sugar

1/2 teaspoon salt

2 teaspoons baking powder

1/3 cup vegetable oil

1 egg

1/3 cup milk

1/4 apple butter

1 cup fresh blueberries

1/2 cup white sugar

1/3 cup all-purpose flour

1/4 cup butter, cubed

1 1/2 teaspoons ground cinnamon