Preheat oven to 350 degrees F. Line an 8x8 inch pan with parchment paper and generously spray with nonstick cooking spray. Set aside.

Make the base + topping: In a large bowl, use a fork to mix together the oat flour (or flour), oats, coconut or brown sugar, baking soda, salt and lemon zest, if using. Add in melted butter, vanilla extract and almond extract and stir until a nice crumble forms and dough begins to clump together.

Place 1 3/4 cups of the mixture into the prepared pan and place the remaining mixture into the fridge (the remaining mixture will be used for the topping). Use your hands to evenly press the dough to the bottom of the pan.

Next make your raspberry filling: place a medium pot over medium heat. Add in raspberries, maple syrup, vanilla extract, tapioca flour or arrowroot, lemon zest and juice, if using, and salt. Use a wooden spoon to press down and break down the raspberries just a bit.

Bring to a boil, then reduce heat to a simmer and cook for 3-5 more minutes until mixture is thickened up and nicely coats the back of a wooden spoon. Pour mixture over the crust and use a spoon to spread evenly over the base.

Take the remaining topping out of the fridge. By now there should be some nice crumbles that have clumped together. Sprinkle the topping over the filling.

Bake for 30 minutes or until the filling is bubbly and the topping is golden. Allow bars to cool completely on a wire rack before transferring to the fridge to chill. Bars are delicious served at room temperature or straight out of the fridge. Use a sharp knife to cut into 12 or 16 bars before serving.