Preheat oven to 375℉. Grease a 12-cup muffin pan with cooking spray.
Make streusel by combining flour, brown sugar, and cinnamon in a medium bowl. Cut in the 2 tablespoon of butter with a pastry cutter or two knives until the mixture is crumbly. Set aside for later.
In a small bowl, combine diced pears and two tablespoons of gluten free flour. Set aside.
In the bowl of the stand mixer combine softened butter and white sugar. Mix well. Add eggs, one at a time, beating at low speed after each addition. Scrap down sides of bowl repeatedly and keep mixing.
While the butter, sugar, and eggs are mixing, combine gluten free flour, baking powder, salt, and cinnamon in a separate bowl. Whisk to combine.
Add dry ingredients and milk alternately to the butter mixture, beginning and ending with dry ingredients. Mix until just combined.
Gently stir in reserved pears. Spoon into prepared pan. Sprinkle about a tablespoon of streusel over batter of each muffin.
Bake for 18-25 minutes, until golden. Let cool in pan for about 5 minutes, then gently remove muffins from pan to a wire rack to cool. Serve warm.