Preheat the Oven: Preheat your oven to 350°F (175°C). Lightly grease a muffin tin or line it with paper liners for easy removal.
Mix Dry Ingredients: In a large mixing bowl, combine rolled oats, cinnamon, nutmeg, baking powder, salt, and nuts (if using). Stir to ensure the spices are evenly distributed.
Combine Wet Ingredients: In a separate bowl, whisk together almond milk, applesauce, maple syrup (or honey), egg, and vanilla extract until smooth.
Bring It All Together: Pour the wet ingredients into the dry ingredients and stir gently until fully combined. Fold in the diced apples, making sure they’re evenly distributed.
Fill the Muffin Tin: Using a spoon or measuring cup, divide the oatmeal mixture evenly into the muffin cups, filling them about ¾ full. Press down gently to compact the mixture.
Bake to Perfection: Place the muffin tin in the preheated oven and bake for 20-25 minutes or until the tops are golden brown and a toothpick inserted into the center comes out clean.
Cool & Serve: Allow the oatmeal cups to cool in the pan for 5 minutes before transferring them to a wire rack. Enjoy warm, or let them cool completely before storing.