Prep the pan and oven: Heat the oven to 350°F (175°C). Grease a 9x5-inch loaf pan and line it with a parchment sling for easy removal.
Prep the apples: Peel if you prefer (peels are fine too).
Core and dice into small cubes, about 1/4–1/2 inch. You’ll want about 1 1/2 cups of apple.
Mix the dry ingredients: In a large bowl, whisk flour, granulated sugar, brown sugar, baking powder, baking soda, salt, cinnamon, and nutmeg until evenly combined.
Mix the wet ingredients: In a separate bowl, whisk eggs, yogurt, oil, and vanilla until smooth.
Combine gently: Pour the wet mixture into the dry. Stir with a spatula until just a few streaks of flour remain.
Fold in the diced apples. Do not overmix.
Pan and top: Scrape the batter into the prepared pan and smooth the top. Sprinkle with coarse sugar or cinnamon-sugar if using.
For a pretty finish, you can fan a few thin apple slices on top.
Bake: Bake for 50–60 minutes, or until the top is golden and a toothpick inserted in the center comes out clean or with a few moist crumbs. If the top browns too quickly, tent loosely with foil for the last 10–15 minutes.
Cool: Let the loaf cool in the pan for 15 minutes, then lift it out and cool completely on a wire rack before slicing. This helps it set and slice cleanly.
Serve: Enjoy plain, with a pat of butter, or lightly warmed.
It’s even better the next day as the flavors meld.