cinnamon streusel topping

1. In a medium bowl, combine sugar, cinnamon, salt, flour, oats, butter with your fingers until well mixed. Mix in pecans and set aside.

cinnamon filling

1. In a small bowl, combine melted butter, brown sugar and cinnamon and stir until well mixed. Set aside while you make the muffin batter.

cinnamon muffins

1. Preheat oven to 350°F. Line a 12- cup muffin pan with liners and set aside.
2. Whisk together flour, baking powder and baking soda in a medium bowl and set aside.
3. In the bowl of a stand mixer fitted with a paddle attachment, cream butter, sugar and salt until light and fluffy, about 2 minutes. Mix in eggs one at a time, scraping down bowl as needed. Mix in sour cream and vanilla until just combine. Add dry ingredients and mix until just combined.
4. Spoon batter into prepared muffin cups, filling halfway full. Use the back of a small spoon to make a small well in the center of the batter, then dollop in a scant teaspoon of cinnamon filling. Top with remaining batter and smooth surface as best you can. Sprinkle the streusel mixture on top.
5. Bake for 22- 25 minutes, or until edges of muffin are just golden brown and springy. Let cool in the pan for 5 minutes, then transfer to a cooling rack to cool completely.