Beat the egg whites and cream of tartar with a hand mixer until stiff peaks appear.
In a bowl, whisk together the egg yolks, buttermilk, vanilla and 2 sticks of melted butter.
Into a large bowl stir together the flour, brown sugar, salt, baking soda, baking powder and cinnamon.
Combine with the wet ingredients and mix until incorporated. Fold the whites into the batter, gently.
Grease the waffle iron with a small amount of melted butter and heat the waffle iron according to the manufacturer's instructions.
Ladle batter onto the waffle iron and cook until golden brown, about 3 1/2 to 5 minutes. Repeat with the remaining batter.
For the strawberry sauce:.
In a small pot over medium heat, combine the strawberries, sugar, water, lemon zest, lemon juice and cornstarch. Bring to a simmer and whisk gently until mixture thickens slightly.
Serve waffles with powdered sugar and strawberry sauce.