Preheat your oven to 350°F (175°C). Grease and flour a 9-inch round cake pan or line it with parchment paper.

In a large mixing bowl, combine the flour, sugar, baking soda, baking powder, cinnamon, and salt. Mix well.

In another bowl, whisk together the vegetable oil, applesauce, apple cider vinegar, and vanilla extract until smooth.

Pour the wet ingredients into the dry ingredients and mix until just combined. Do not overmix.

Fold in the diced apples and nuts (if using) until evenly distributed throughout the batter.

Pour the batter into the prepared cake pan and spread it evenly.

Bake in the preheated oven for 30-35 minutes, or until a toothpick inserted into the center comes out clean.

Allow the cake to cool in the pan for 10 minutes, then transfer it to a wire rack to cool completely.

Serve plain or dust with powdered sugar for a finishing touch.