Preheat the oven to 350 degrees F and grab a nonstick muffin pan that holds 12 muffins. Grease if necessary.
Add the dry ingredients to a large mixing bowl and whisk together. Set aside. Then add the wet ingredients to a medium bowl and mix thoroughly to get the cashew butter evenly combined.
Pour the wet mixture into the bowl of dry ingredients and mix until combined. Now gently fold in the blackberries. Use care not to break them.
Divide the batter among your 12 muffin tins and bake for 22-24 minutes, until a toothpick comes out mostly clean, and the edges of your muffins appear golden.
Remove from the oven and let rest for at least 10 minutes to completely set, before removing the muffins from the pan.
Notes
For accuracy, it's best to weigh your flour. But if you don't have a kitchen scale, use 2.5 cups, and spoon and level the flour into your measuring cup.Blanched almond flour works best, so don't sub for almond meal or non blanched flour.Make sure your baking powder is fresh and still active. Baking powder that has been open in your pantry for 6+ months will start to lose its effectiveness.Use fresh blackberries rather than frozen. Frozen blackberries may bleed into your batter turning it purple and adds extra liquid.Be gentle when folding in the blackberries to prevent them from breaking into your batter.Give your muffins enough time to cool in the pan, before transferring them. Almond flour desserts can be softer and delicate so it's easiest to remove them once slightly cooled.Leftovers keep at room temperature for 2-3 days, refrigerated for 5-6 days, or freeze for up to 3 months.