Heat waffle maker. In large bowl, stir together flour, salt, baking soda and cinnamon; set aside.
In small bowl, beat egg whites and cream of tartar with electric mixer on high speed until stiff peaks form; set aside. In medium bowl, beat egg yolks, buttermilk, 1/4 cup melted butter, the syrup and vanilla; set aside.
Make well in center of flour mixture. Add egg yolk mixture; mix just until combined. Fold in beaten egg whites.
Spray waffle maker lightly with cooking spray. Spoon batter onto hot waffle maker, following manufacturer’s directions for recommended amount. Close lid of waffle maker; bake 3 to 4 minutes or until steaming stops and waffles are golden brown. (To make ahead, place waffles on ovenproof plate in 200°F oven until ready to serve.)
In another small bowl, beat 2 tablespoons melted butter, milk and powdered sugar until smooth. (You may have to add more milk til smooth) Drizzle over waffles. Serve remaining glaze on the side.