Add butter, sugar, brown sugar, salt, and cinnamon to a bowl and mix until combined.
Add flour and mix until combined. Set aside
Prepare the Muffins
Preheat oven to 350℉.
In a bowl, cream butter and sugar together.
Add eggs and whisk until combined. Add sour cream, buttermilk, vanilla extract, salt, baking soda, and baking powder and whisk until fully combined.
Fold in 2 cups of flour until just combined.
In a separate bowl toss chopped pear with 1 tbsp flour to coat.
Add pear to the muffin batter and gently fold the batter until the fruit is evenly dispersed.
Grease or line a muffin pan with cupcake wrappers.
Add a spoonful of batter to each muffin well.
Take about ⅓ of the streusel and divide it evenly over the muffin batter in each well.
Divide the remaining batter evenly among the muffin wells.
Crumble the remaining streusel over each muffin, dividing it evenly.
Bake muffins for 18 - 22 minutes or until edges have browned and a toothpick inserted in the center comes out clean or with a few moist crumbs.
Allow the muffins to cool in the pan for 3-5 minutes before transferring to a wire rack to cool completely.
Notes
A Note on Room Temperature Ingredients: room temperature ingredients mix together easily, creating a smooth batter and a more consistent texture in the final muffin.