To make the filling, bring blueberries, applesauce, maple syrup, and lemon juice in a medium saucepan over medium heat.
Bring to a boil and reduce heat to simmer until sauce is thick around 10 minutes. Remove from heat and allow to cool.
In the meantime, Preheat the oven to 375°F. Line an 8×8 baking dish with parchment paper and spray with cooking oil. Set aside.
In a large bowl, add oats, buckwheat flour, almond meal, flaxseeds, baking powder, and salt. Mix maple syrup, coconut oil, and vanilla in a smaller bowl.
Stir in the liquid mixture, and into the dry ingredients until thoroughly combined.
Set aside 1/3 of the base and press the remaining 2/3 in the base of the prepared pan. Spoon blueberry jam on top of the base and spread evenly using a spoon.
Sprinkle the remaining oat mixture on top. Bake for 30 minutes or until the top is golden brown. Remove from oven and allow to cool before cutting into bars.