Preheat a Belgian waffle maker. Whisk the all-purpose flour, cornstarch, granulated sugar, baking powder, and fine salt in a large bowl.
Whisk the whole milk, neutral oil, and vanilla extract in a separate bowl. Pour this mixture into the dry ingredients and stir just until combined.
Beat the aquafaba and cream of tartar with an electric mixer for 4 to 6 minutes, until thick, glossy peaks form.
Fold one-third of the whipped aquafaba into the batter to loosen it. Gently fold in the remainder in two additions, preserving as much air as possible.
Lightly coat the waffle maker with the remaining neutral oil. Add the amount of batter recommended for the appliance and cook until the waffle is deeply golden and steam has mostly stopped escaping.
Place each finished waffle directly on a cooling rack so the exterior remains crisp. Repeat with the remaining batter and serve the waffles while warm.
