These Coffee Cake Muffins have a cinnamon streusel swirl filling as well as a deliciously crumbly pecan streusel topping.
Line a 12 cup muffin or cupcake tin with paper liners
Adjust oven rack to middle position and heat oven to 375 degrees
In a food processor, pulse 5 Tablespoons granulated sugar, light brown sugar, flour, butter, and cinnamon about 5 pulses, until mixed.
In a small bowl, reserve 3/4 cup of this streusel mixture for filling. Leave the rest in food processor.
Add pecans and remaining 3 Tablespoons granulated sugar to food processor and pulse until pecans are coarsely ground, about 6 pulses. Transfer to another bowl to use for topping.
To empty food processor (no need to wash), add flour, sugar, butter, baking powder, and salt and pulse about 10 times until mixture looks like sand. Transfer to a large bowl.
In a medium bowl, whisk sour cream, eggs, and vanilla.
Using a rubber spatula, gradually fold wet ingredients into flour mixture until combined. Do not overmix.
Add about 1 Tablespoon batter to each muffin cup. Add 1 Tablespoon streusel filling mixture (the one without pecans) , pressing lightly with back of spoon. Top with remaining batter. Place streusel topping on each muffin cup, pressing gently into batter.
Bake for about 20 minutes or until toothpick tester comes out clean, rotating pan halfway through cooking time.
Allow to cool in muffin tin for 30 minutes. Then, transfer to wire rack to cool completely.
Store covered at room temperature for up to 3 days