Step 1: Preheat your oven to 180°C (350°F). Grease a standard loaf pan or line it with parchment paper for easy removal.
Step 2: In a large mixing bowl, combine the grated apples with the plain unsweetened yogurt and eggs. Stir until these wet ingredients are well combined.
Step 3: Add the rolled oats, ground cinnamon, and baking powder to the wet mixture. If you are using vanilla extract and chopped walnuts, add them now as well.
Step 4: Stir everything together with a spoon or spatula until all the dry ingredients are fully incorporated into the wet mixture and no streaks of flour remain. Be careful not to overmix.
Step 5: Pour the batter evenly into the prepared loaf pan. Use a spatula to gently smooth the top surface of the loaf.
Step 6: Bake for 30–35 minutes, or until a wooden toothpick inserted into the center of the loaf comes out clean. The top should be golden brown.
Step 7: Once baked, remove the loaf from the oven and let it cool in the pan for about 10-15 minutes before carefully removing it and transferring it to a wire rack to cool completely.
Step 8: Slice and serve warm or at room temperature. This loaf is delicious on its own or with a light spread.