1. Whisk together flour, salt, and cinnamon. Whisk in butter, milk, and vanilla. Whisk in 3/4 cup sugar. Beat egg whites with an electric mixer on high speed until foamy. Add remaining 1 tablespoon sugar and beat until stiff peaks form. Fold egg whites into flour mixture.

2. Heat waffle-cone iron to medium; coat with cooking spray. Spoon about 1/4 cup batter onto iron. Using a small spatula, spread batter slightly. Close lid and cook 1 minute before lifting the lid to check for doneness. Continue cooking until desired color is reached, about 1 to 1 1/2 minutes more on medium heat.

3. Remove waffle from iron and press into a small bowl to shape. Let stand until cool. Repeat with remaining batter. Waffle-cone bowls can be made up to 1 week ahead and stored in an airtight container at room temperature.