Preheat oven to 350 degrees Fahrenheit (175 degrees Celsius).
Place muffin liners in a regular size 12 cup pan. I prefer to use reusable silicone liners.
In the bowl of a stand mixer, add the softened butter, the peanut butter and the coconut sugar
Beat on medium-high until mixture becomes fluffy and a very light tan in color (about 4 minutes)
In the meantime, in a large bowl, mix together the almond flour, coconut flower, baking powder and salt. Set aside.
When the butter mixture is ready, add the egg, milk and vanilla extract and beat on low speed until combined.
Pour the wet butter mixture into the bowl with the dry ingredients and mix until well combined.
Use an ice cream scoop or a spoon to fill the liners about 1/2 to 2/3 of the way.
Using a spoon, push the dough against the sides of the cup to form a small hole in the middle. This is where you'll be placing the apples
Wash the apple and dice it into small pieces. About 1/4 inch cubes.
Place the apple pieces into the holes you made in the middle of the cups.
Sprinkle with cinnamon and nutmeg
Bake in the preheated oven for 25 minutes
Serve warm with a drizzle of lemon juice on top