Preheat oven to 350°F (175°C). Generously coat a muffin pan with cooking spray. Measure and set out your egg and yogurt to reach room temperature. Melt coconut oil, measure, and set aside to reach room temperature.
In a large bowl, add the muffin dry ingredients—flour (use a food scale if you have it—135g), cornstarch, baking powder, salt, cinnamon, nutmeg, and allspice. Mix until combined.
In a separate bowl, whisk together the muffin wet ingredients—egg, Greek yogurt, melted coconut oil (see note 2), vanilla extract, and brown sugar. Whisk together until smooth.
Peel and very finely chop the apple. Toss with the lemon juice. Add to the dry ingredients and stir until the apple pieces are coated in flour.
Add dry ingredients on top of wet. Mix with a spatula until ingredients are combined and no dry streaks of flour remain.
Use a 1/4 cup measuring cup to scoop the batter into each of the sprayed muffin cups. There should be enough batter for about 10 muffins.
In another bowl, toss together the Cinnamon Sugar Topping dry ingredients—flour, quick oats, cinnamon, and brown sugar. Pour in the coconut oil and mix to combine, crumble with your fingertips if needed.If the mixture is too wet, add flour; if it’s too dry, add coconut oil.Sprinkle this topping evenly on top of each muffin. Don’t press the topping into the muffin.
Bake for 20–25 minutes or until a toothpick when inserted in the center of the muffin comes out clean. Remove the pan from oven and allow to cool for 5 minutes before taking the muffins from the tin. Use a spoon or butterknife to trace around the edges and coax the muffins out. Allow muffins to finish cooling on a cooling rack so the bottoms don’t get soggy. Enjoy warm!
Notes
Note 1: Feel free to increase the spices if desired. As written, the spices yield a very subtle flavor.Note 2: Measure the coconut oil in its melted form. Do not add hot or warm coconut oil to the wet ingredients; wait until it’s a room temperature so it doesn’t clump.Note 3: I love to use Granny Smith or Honey Crisp!Storage: Store completely cooled muffins in an airtight container in the fridge. Warm in the microwave for 10–15 seconds before serving. Muffins are best enjoyed within 2–3 days.