Preheat the oven to 350℉. Generously grease an 8" springform pan.
Peel and core the apples. Cut into quarters. Slice quarters into thick slices, then, cut the slices in half, so you have chunks of apple that are 1/4-1/2"" thick and about 1½" long.
Melt the butter. Set aside to cool.
In small bowl, mix dry ingredients. Set aside.
In a medium bowl, whisk the eggs until they are foamy, about 1 minute.
Add in the sugar and whisk until well combined and frothy, 1-2 minutes.
Whisk in the Vanilla and Calvados. Whisk until blended.
Next, whisk in half of the flour mixture until combined. Follow with half of the melted butter. Whisk to combine. Follow by the last half of the flour. Whisk to combine. Finally, add the last half of the melted Butter. Whisk gently until combined an you have a smooth batter.
With a rubber spatula, gently fold in the apple pieces. Mix until apples are well combined and coated.
Gently scrape the batter into prepared pan. Push and press the apples around to settle into the pan. Use spatula to make top as level as possible.
Place on parchment-lined baking sheet. Place in oven. Bake for about an hour, checking at 50 minutes, or until top is golden and a knife inserted into the center comes out clean.
Remove from oven. Let cool in pan for 5-10 minutes, then carefully run a knife around the edge of the pan and release the springform pan.
Allow cake to cool until slightly warm, or to room temperature.