Preheat oven to 350F. Sift together dry ingredients. Set aside.
In another bowl, beat egg and sugar until thickened, about 3 minutes. Add remaining wet ingredients to egg mixture and beat on low speed until combined. Add ⅔ of the dry ingredients and stir to combine.
Pour apple pieces into remaining dry ingredients and toss to coat. (This will prevent apples from sinking to the bottom of the muffins.) Stir gently into batter.
Distribute batter evenly among 9 lined muffins tins. Bake 13-15 minutes, or until a toothpick inserted removes cleanly.
Enjoy as is, or top with a dallop of vanilla yogurt or cream cheese frosting.
Recipe by Jellibean Journals at https://jellibeanjournals.com/iron-cupcake-earth-apples/