Heat the oven to 350°F degrees with the rack in the middle. While the oven is heating, line a standard muffin pan with parchment paper liners or grease well with ghee or coconut oil.
In a medium bowl, combine the almond flour, ground cinnamon, baking soda, cream of tartar, and kosher salt. Whisk it all together.
In a separate large bowl, use an electric mixer or whisk to combine the coconut sugar, eggs, and vanilla. Mix until the sugar has dissolved.
Add the dry ingredients to the bowl of wet ingredients and use a hand mixer or whisk to blend until well combined. Next, use a spatula to fold the shredded apple into the batter until well mixed.
Divide the batter evenly into each muffin liner. I use a #20 disher (3 tablespoons) to scoop the batter.
Add a sprinkling of paleo streusel on top of each muffin (about a tablespoon). Use your fingers to press the topping gently into the batter so it doesn't fall off after baking.
Bake the muffins in the oven at 350°F for 22 to 25 minutes, rotating the muffin tray at the halfway mark. The muffins are done cooking when the toppings are golden brown and a toothpick inserted into the middle comes out clean.
Remove the muffins from the oven and transfer the muffins to a wire rack to cool completely.