BROWN THE BUTTER: In a small skillet, melt all 11 tablespoons of the butter over low heat. Continue to simmer the butter until it turns a dark golden amber color and has a caramel fragrance. Pour the browned butter into a bowl or measuring cup and allow to cool.
PREPARE: Preheat oven to 350° and arrange the oven rack to the center position. Line muffin tin with liners or spray generously with nonstick cooking spray.
MAKE THE CINNAMON PECAN TOPPING: In a small bowl, add the ¼ cup flour, ¼ each brown and granulated sugars, cinnamon, pecans, and salt. Stir the brown butter, then scoop 5 tablespoons into the topping mixture. Use your fingers or a fork to work the mixture into small lumps. Set aside.
COMBINE THE DRY INGREDIENTS: In a large bowl, whisk the flour, baking powder, baking soda, salt, cinnamon, and pumpkin pie spice together until it’s evenly mixed.
COMBINE THE DRY INGREDIENTS: In a medium mixing bowl, stir together the remaining butter, pumpkin, eggs, sour cream, and vanilla, until well-combined. Pour the wet mixture in with the dry ingredients and fold together until all the flour is mixed in.
BAKE: Using a batter scoop or large spoon, fill each muffin cup with about 3 tablespoons of bater, or ⅔ full. Top each muffin with a heaping tablespoon of the cinnamon pecan topping then bake for 22-25 minutes or until a toothpick comes out of the center with only a few crumbs.
COOL: Allow the muffins to cool about 3 minutes in the muffin tin, then transfer to a cooling rack to finish cooling completely.