Preheat your oven to 350 degrees f. and line an 8x10 rimmed baking pan with parchment paper.
In a large bowl, whisk to combine all dry ingredients.
In a second bowl, add all wet ingredients and whisk until thoroughly combined.
Pour the wet over the dry ingredients and whisk to combine everything well.
Add in any extras if desired (dried fruits and chopped nuts of choice), and using a silicone spatula, stir to incorporate the into the batter.
Scoop your batter into the prepared baking pan and spread evenly.
Place into the oven and bake for 33-35 minutes, or until golden-brown. Allow it to cool on wire rack while making your frosting.
In a food processor add the peanut butter, coconut butter, maple syrup, vanilla, salt, and then pulse a few times, until smooth.
Evenly and gently spread your creamy peanut butter frosting over your cooled apple bars. You might need to use an angled pastry spatula to get into those corners.
Slice into bars and serve.
Store any leftovers in your refrigerator in an air-tight container for about 5-6 days.