Rhubarb Waffles with Rhubarb Sauce

To prepare sauce: Combine rhubarb and 1 1/2 cups sugar in a medium saucepan and bring to a simmer over medium-low heat. Cook until the rhubarb is tender and translucent. Transfer about 1 cup of the rhubarb to a small bowl with a slotted spoon, and reserve for the waffle batter. Boil the remaining rhubarb in syrup over medium heat, stirring occasionally, until slightly thickened, 5 to 7 minutes.

To prepare waffles: Whisk egg whites in a large bowl until frothy. Whisk in milk and oil. Stir in the reserved 1 cup cooked rhubarb. Sift all-purpose flour, whole-wheat flour, 3 tablespoons sugar, baking powder and salt into a medium bowl. Gently stir the dry ingredients into the egg-milk mixture just until moistened.

Preheat a waffle iron. (If your waffle iron is not nonstick, brush it lightly with oil.) Fill the iron about two-thirds full. Close and cook the waffles until they are nicely browned, about 4 minutes. Repeat with the remaining batter, coating the waffle iron lightly with oil, if necessary, before cooking each batch. Serve hot, topped with the rhubarb sauce.