Preheat your oven to 350°F (175°C). Grease your 9-inch round cake pan with butter or oil and line it with parchment paper for easy removal (optional).

Grate the apple finely using a grater and immediately toss it with the lemon juice to prevent browning. Set aside.

In a medium bowl, whisk together the all-purpose flour, cocoa powder, baking powder, baking soda, and salt. Set this bowl aside.

In another large bowl, whisk together the sugar, vegetable oil, and eggs until well combined. Add in the milk and vanilla extract, and mix until smooth.

Gradually add the dry ingredients into the wet mixture, stirring until fully combined. Be careful not to overmix; just stir until smooth.

Gently fold the grated apple and semi sweet chocolate chips into the batter using a rubber spatula.

Slowly pour in the hot water and stir until the batter is smooth and slightly runny. This will help create a moist and tender cake.

Pour the batter into the prepared cake pan and smooth the top. Bake in the preheated oven for 35-40 minutes, or until a toothpick inserted into the center comes out clean or with a few moist crumbs.

Once baked, remove the cake from the oven and allow it to cool in the pan for about 10 minutes. Afterward, transfer it to a wire rack to cool completely.

Slice the cake into 8-10 slices and enjoy! You can also dust it with powdered sugar or drizzle with a chocolate glaze for an extra treat.