Preheat oven to 350 degrees F. In a large mixing bowl combine flour, oats, white sugar and brown sugar, cinnamon, baking powder and a pinch of salt. Mix together. Then add cubed butter and use your hands to rub the butter into the flour mixture until it forms a crumbly texture. Set aside.
In a small sauce pan combine chopped dates with water, lemon juice and vanilla extract. Stirring frequently, cook on medium low for 5-6 minutes until a paste is formed. Remove from the heat and allow to cool down for about 10 minutes.
Line a baking pan with parchment paper. Reserve about 1 cup of the crumble mixture and pour the remaining into the pan pressing it down into an even layer. Pour the cooled date mixture on top of the crust and spread evenly. Then sprinkle the remaining crumble over the top. Bake at 350 degrees F for around 45 minutes until golden brown. Remove from the oven and allow to cool. Then slice into bars and enjoy!