For the Streusel: Pulse 5 TBSP of granulated sugar, brown sugar, flour, cinnamon and butter in a food processor until just combined. Reserve 3/4 cup sugar mixture for cinnamon filling.
Add pecans and remaining granulated sugar to food processor with remaining sugar mixture and pulse until nuts are coarsely ground. Transfer to a bowl and set aside for streusel topping. Do not wash food processor yet.
For the muffins: Adjust oven rack to middle position and heat oven to 375°F Grease muffin tin with cooking spray and line with paper liners.
Whisk eggs, sour cream, and vanilla in bowl. Pulse flour, sugar baking powder, salt and butter in food processor until mixture resembles wet sand. Transfer to large bowl.
Using a rubber spatula, gradually fold in egg mixture until just combined. Place 1 TBSP of batter in each muffin cup and top with 1 TBSP of cinnamon filling. Using back of spoon, press cinnamon filling lightly into batter, then top with remaining batter. Sprinkle streusel topping evenly over batter.
Bake until muffins are light golden brown brown and tooth pick inserted into center comes out with a few dry crumbs (about 22-28 minutes) Cool muffins in tin for 30 minutes, then carefully transfer to rack to cool.