COMBINE FLOUR, BAKING POWDER, sugar, salt and cashews in a mixer. Add the eggs and buttermilk and mix at medium speed until smooth. Add the melted butter and mix until incorporated. In another bowl, beat the egg whites until stiff and fold into the batter. Heat your waffle iron and cook your waffles as usual.
BLUEBERRY TOPPING: COMBINE THE SUGAR, LEMON AND WATER in a 1 quart pot and cook over medium heat until the sugar melts. Pour in the blueberries and cook, stirring, for 1 minute. Pour into a bowl and let cool before serving.