Bring blueberries,1/2 cup apple juice and sugar to boil in heavy medium saucepan. Simmer over medium heat until reduced to 2 cups, about 15 minutes. Dissolve 1 tbsp cornstarch in remaining 2 tbsp apple juice and add to blueberry mixture. Add lemon juice. Bring to boil,stirring constantly;simmer until thick, about 1 minute. Cool slightly. (Can be made 2 days ahead. Cover and refrigerate. Rewarm over medium-low heat before serving)
2For Lemon poppyseed waffles:
Whisk first 6 ingredients in large bowl to blend. Whisk eggs,buttermilk,melted butter and lemon peel in small bowl to blend. Add buttermilk all at once to flour mixture and whisk until just blended. Let mixture stand 15 minutes.
3Preheat waffle iron according to manufacturer's instructions. Spoon batter onto waffle iron. Cover and cook until golden and cooked through about 7 minutes (cooking time may vary, depending on waffle iron). Repeat with remaining batter. Serve immediately with warm blueberry sauce.