Combine in a large bowl, the pumpkin puree, eggs, and brown sugar. Whisk these ingredients until smooth.
Add the milk, yogurt and vanilla to the pumpkin mixture. Whisk until smooth.
In a separate bowl, mix together the flour, cinnamon, nutmeg, salt, and baking powder.
Add the dry ingredients to the wet ingredients. Stir in the flour until just combined, but still slightly lumpy.
Use a rubber spatula to fold in the chopped pecans. Let the batter rest for five minutes. Meanwhile, preheat the waffle iron.
Once hot, spray the inside of the waffle iron with non-stick spray. Ladle the recommended amount of batter for your iron. Use 1 cup of batter for most 7 inch waffle machines. Bake as per your waffle iron's instructions.