Preheat the oven to 300°F.
Place the dates in a medium bowl and cover with hot water.
Set aside to soak for 20 minutes.
Drain any excess water from the bowl and transfer the dates to a food processor.
Add the applesauce, lemon juice, vanilla and blend into a paste. Set aside.
In a large bowl, stir together the rolled oats, oat flour, hazel nuts, lemon zest, cacao, baking soda, baking powder and salt.
Add the date and applesauce paste and mix well. The mixture should be on the dry side.
Scoop a large tablespoon of dough, roll it into a ball and then pat it flat on a baking sheet.
Bake until the tops of the cookies appear crispy and browned, 30 to 40 minutes.
Transfer to a wire rack to cool.