Preheat your oven to 350℉. Grease a tube pan then lightly coat with flour. Tap the pan over the sink to remove the excess flour.
Prepare the apple filling: combine the apples, sugar, cinnamon, and all-purpose flour in a small bowl and stir to combine. Set aside.
In a large bowl, add the flour, baking soda, sea salt, and cinnamon, and whisk to combine.
Add the remaining cake batter ingredients - granulated sugar, vegetable oil, non-dairy milk, apple cider vinegar, orange juice, and vanilla extract - to the large bowl. Whisk gently to combine, stopping as soon as the batter is mostly smooth, with few or no lumps.
Reserve about ¼ cup of the apple filling, and pour the rest into the bowl with the batter. Use a wooden spoon or rubber spatula to fold in the filling.
Pour the cake batter into the tube pan, then tap it lightly on the counter to eliminate air bubbles. Sprinkle the reserved ¼ cup of apple filling over the top of the cake, then sprinkle the 1 teaspoon granulated sugar over the top (if using).
Bake for 60-65 minutes, until the cake is golden brown and a toothpick comes out clean. Allow the cake to cool most of the way in the pan, then carefully turn it out onto a wire rack.