Preheat your oven to 350°F (175°C). Grease a 9x5-inch loaf pan or line it with parchment paper.
In a large mixing bowl, combine the flour, sugar, baking powder, baking soda, and salt. Whisk together until well mixed.
In another bowl, cream the softened butter until light and fluffy. Add the eggs one at a time, mixing well after each addition. Stir in the vanilla extract and sour cream until fully combined.
Gradually add the wet ingredients to the dry ingredients, mixing until just combined. Be careful not to overmix.
Gently fold in the cherries and walnuts (if using) until evenly distributed throughout the batter.
Pour the batter into the prepared loaf pan and smooth the top with a spatula.
Bake in the preheated oven for 55-65 minutes, or until a toothpick inserted into the center comes out clean.
Allow the bread to cool in the pan for about 10 minutes before transferring it to a wire rack to cool completely.