Preheat the oven to 350°F and line an 8×8 or 9×9 inch baking pan with parchment paper.
In a food processor, pulse together 2 1/2 cups of the oats and all of the almonds until they are ground into a flour-like consistency.
Once complete, transfer the oat and almond mixture to a large mixing bowl, add the remaining rolled oats, baking powder, cinnamon and salt and stir to combine.
Add the cold butter and honey and use a wooden spoon or spatula to incorporate it with the oat mixture until well combined and the dough is sticky. (You can also do this with your hands if you prefer, I find it works better).
Once complete, add two-thirds of the dough to the baking pan and use your hands to press it firmly into the bottom. Set aside.
In a small pot on medium heat, add the raspberries, vanilla extract, lemon zest, salt and honey. Use a wooden spoon to gently break up the raspberries (you can leave some chunks but you want them mostly broken down) and allow to heat gently for 3-4 minutes until raspberries become slightly liquidy.
Once heated, add tapioca or arrowroot powder and heat for another 1-2 minutes, stirring frequently, until the mixture has thickened.
Once the raspberry mixture is ready, transfer it to the baking pan and use a spatula to spread it evenly across the base, and then top it with remaining oat mixture.
Transfer the pan to the oven to bake for 30-35 minutes until raspberry mixture is bubbling and the top is golden brown.
Remove from the oven and allow to cool completely before slicing into 9 bars.
The bars can be stored in the fridge for up to 5 days or in the freezer for a month.