Preheat your oven to 350°F (175°C). Grease and flour a 9×5-inch loaf pan or use parchment paper.

In a bowl, whisk together the flour, baking powder, baking soda, salt, cinnamon, and nutmeg. Set it aside.

In a large bowl, use an electric mixer to cream the softened butter and sugar together until it’s light and fluffy.

Beat in the eggs one at a time, ensuring each is fully incorporated before adding the next. Mix in the vanilla extract.

Gradually add the dry ingredient mixture to the wet mixture, alternating with diced plums, until everything is just combined. Be careful not to over-mix!

If using, fold in the chopped walnuts or pecans gently.

Transfer the batter into your prepared loaf pan and smooth the top with a spatula.

Place the pan in the preheated oven and bake for 50-60 minutes, or until a toothpick inserted in the center comes out clean.

Once baked, allow it to cool in the pan for 10 minutes before transferring it to a wire rack to cool completely.