Preheat your oven to 350 degrees Fahrenheit and position a rack in the center. Line a 9-inch round or 8x8-inch square pan with parchment paper, or spray it generously with cooking spray.

In a large mixing bowl, whisk together the all-purpose flour, baking soda, baking powder, ground cinnamon, ground nutmeg, and sea salt until evenly distributed.

Peel, core, and dice the fresh apples into roughly 1/2-inch pieces.

In a medium mixing bowl, whisk together the vegetable oil, large eggs, and vanilla extract until smooth and slightly frothy.

Pour the wet mixture into the dry ingredients and gently fold together with a spatula until just combined, stopping when no flour streaks remain.

Fold the diced apples and hot water into the batter evenly, taking care not to overmix.

Transfer the batter into the prepared pan and smooth the top with a spatula, ensuring the batter fills the corners evenly.

Bake the cake for 48 to 55 minutes, or until a toothpick inserted in the center comes out with just a few moist crumbs.

Allow the cake to rest in the pan on a cooling rack for 15 minutes to set the crumb.

Run a thin knife around the edges, invert the cake onto a cooling rack, remove parchment paper, and let cool completely for about 1 hour before slicing or glazing.