In a large bowl stir together the oat flour, coconut oil, coconut sugar, applesauce, cinnamon, baking soda, and salt. Add in the vinegar and stir quickly-- you should see the batter get slightly fluffier from its reaction with the baking soda.
Fold in the coconut, if using, carrots, and pineapple. The batter will most likely be thicker than traditional muffin batter, but that's okay! Use a 1/4 cup to scoop the batter into the 12 muffin cups.
To prepare the crumble, stir together the flour, sugar, coconut, cinnamon, salt, and oil. Use you fingers to sprinkle the mixture evenly over the 12 muffin cups, the gently press the crumble down into the batter to help it stick.
Bake until the tops feel firm to the touch, about 30 minutes. Allow to cool completely before serving.
If you'd like to add a little extra flair to these muffins and don't need them to be nut-free, prepare the cashew glaze by stirring together the cashew butter, maple syrup and lemon juice. Add water one teaspoon at a time until just thin enough to drizzle over the muffins. Use a spoon to drizzle a teaspoon or so over each muffin right before serving.
These muffins are best stored without the cashew glaze on top, and will last a week when stored in an airtight container in the fridge.