Preheat your oven to 350°F (175°C) and position the rack in the middle. Grease a 9×5-inch loaf pan with butter, then line with parchment paper, leaving an overhang on the long sides for easy removal.
In a medium bowl, whisk together the flour, baking powder, baking soda, salt, cardamom, cinnamon, and nutmeg.
In a larger bowl, whisk the eggs and sugar vigorously for about 1 minute until pale and slightly thickened. Add the melted butter (or applesauce), Greek yogurt, and vanilla extract, whisking until fully combined.
Gradually add the dry ingredients to the wet ingredients, folding gently with a spatula. Stop mixing as soon as no dry streaks remain.
Gently fold in the diced apples, ensuring they're evenly distributed throughout the batter.
In a small bowl, mix the sugar, cardamom, and cinnamon for the topping.
Pour the batter into the prepared loaf pan and smooth the top with a spatula. Sprinkle the cardamom sugar mixture evenly over the surface.
Bake for 55-60 minutes, or until a toothpick inserted into the center comes out clean with a few moist crumbs. If the top browns too quickly, tent with foil after 40 minutes.
Allow the bread to cool in the pan for 15 minutes. Then, using the parchment paper overhang, lift the bread out of the pan and place on a wire rack to cool completely.