Combine the flour, cornstarch, brown sugar, baking powder, pumpkin pie spice, ground cinnamon, and salt in a large bowl.
Add the whole milk, pumpkin puree, canola oil, egg, and vanilla. Whisk until combined. Fold in the chopped pecans. Set aside to rest.
Preheat the waffle maker. Once it is hot, grease it, pour 3/4 cup of batter onto it (or the appropriate amount for your waffle maker), and spread it out evenly.
Cook for 4-5 minutes (depending on your waffle iron) until it stops steaming and the waffles are fully cooked.
Remove the waffles, place them on a cooling rack, and repeat with the remaining batter.
Video
Notes
Storage: Place cooled waffles in an airtight container or storage bag with parchment paper between layers. Store in the fridge for 2-3 days or in the freezer for up to two months.