Preheat the oven to 350F.
Grease an 8- by 8-inch baking pan with butter and line it with parchment paper.
Place the cashew or almond butter, eggs, melted butter, and vanilla extract in a food processor and blend until combined.
Add the coconut sugar, almond flour, coconut flour, baking powder, and salt to the wet ingredients and blend again until smooth.
Remove the food processor bowl from the base and use a spatula to stir in the chocolate chips.
Scoop the batter into the prepared pan and smooth out the top with a spatula. Bake for 20-25 minutes. You'll know the bars are ready when the edges are slightly browned and the center is springy but firm.
When the cookie bars are done, remove the pan from the oven with oven mitts and place the pan on a trivet or hot pad on the kitchen counter.
Let the pan cool for at least 20 minutes, and then remove the cookie bars from the pan, using the edges of the parchment paper to lift them out.
Cut the bars into pieces and serve. Store any leftovers in an airtight container.