Preheat your oven to 350°F (175°C) and grease a loaf pan.
In a bowl, whisk together flour, baking soda, salt, and cinnamon.
In another bowl, cream together the butter and sugar until light and fluffy.
Add eggs one at a time, mixing well after each addition.
Stir in vanilla extract.
Gradually add the dry ingredients to the wet mixture, mixing until just combined.
Fold in the diced apples and nuts if using.
Pour the batter into the prepared loaf pan.
Bake for 50-60 minutes, or until a toothpick comes out clean.
Allow to cool in the pan for 10 minutes before transferring to a wire rack.