Preheat oven to 375 degrees. Lightly butter a 9” springform pan.
In a large mixing bowl, beat together vegan butter and evaporated cane sugar and seltzer until fluffy and light. May look slightly curdled at this point. Don’t panic.
In a separate bowl, combine the flour, baking powder, salt, and nutmeg. Add the dry ingredients and the oat milk alternately to the butter mixture.
Keep a light hand, mix just until the ingredients are combined. Spoon the batter into the pan.
Peel and core the apples. Use your impressive knife skills to slice thinly. Toss the slices with lemon juice to keep them from browning.
Press the apple slices into the batter, keeping them about 1/4 inch apart and core side down. Arrange apples in a circular pattern around the outside edge, like the rays of the sun, and then closer and closer to the center till you run out of room or apples. Scatter the cranberries and candied ginger on top, if using, and finish with a sprinkle of demerara sugar and cinnamon.
Bake for 40 to 50 minutes, or until a cake tester or skewer inserted in the center of the comes out clean and your kitchen smells sweet.
Let cool before unmolding. Finish with powdered sugar and serve with caramel sauce, if desired.