Preheat oven to 350 degrees F. Line a standard 12-cup muffin pan with paper liners. Set aside.
Whisk rice flour, almond flour, flaxseed meal, baking powder, and salt in a medium bowl until no clumps remain. Set aside.
Whisk eggs, lemon zest, lemon juice, 2/3 cup maple syrup, and 2/3 cup of coconut oil in a large bowl.
Add the dry ingredients to the wet and whisk to combine. Add the apple, 1/2 cup almonds, and 1/2 cup oats; mix to combine. Divide the batter among the prepared muffin cups, filling each to the very top.
Mix remaining 1/4 cup almonds, 1/2 cup oats, 1 tbs maple syrup, and 1 tbs coconut oil together in a small bowl to combine.
Sprinkle the topping evenly over each muffin.
Bake muffins for 25-30 minutes, or until tops are golden brown and a toothpick, when inserted into the centers, comes out clean.
Notes: The original recipe calls for oat flour, but I couldn't find this at my grocery store. White rice flour served as a good sub.