Preheat oven to 425°F. Grease or line a muffin tin and set aside.
Peel apples and dice into 1/2" pieces or smaller.
In a medium bowl combine flour, cinnamon, nutmeg, baking powder, baking soda, and salt. Add diced apples to dry ingredients and toss to coat. Set aside.
In a large bowl combine eggs, sugar, coconut oil, yogurt, and vanilla.
Add dry ingredients in with wet and gently stir until just combined. Do NOT over mix. (Over mixing causes dry, tough muffins.)
Evenly divide into muffin tin. Fill each cavity to the top.
For the crumb topping: combine flour, sugar, oats and cinnamon. Add cold butter and combine until fine crumbs.
Evenly divide crumb topping between muffins.
Bake at 425° for 5 minutes.
Turn oven down to 350°F and continue baking for 10-12 minutes.
Muffins should be slightly browned and toothpick inserted into the center comes out clean.
Let cool in pan 5 minutes before removing to a cooling rack. ENJOY!