Grease a 9 x 13 casserole dish and set aside.

Place the zest, flour, sugar, ground walnuts, and cinnamon in a bowl. Whisk to combine.

Cut the butter into the mixture in small pieces and use your hands to mix everything together, rubbing it between your palms to create streusel crumbs.

Cover the bowl loosely with clean kitchen towel and place in the refrigerator.

Preheat the oven to 425 F.

Peel and core the apples. cut them into rings a little less than 1/2 inch thick.

Lay the apple rings down into the prepared casserole dish.

Sprinkle apple brandy on top.

In a separate bowl, whisk together the sour cream and heavy cream.

Spread the cream mixture over the fruit in the dish.

Remove the streusel from the refrigerator and scatter it evenly over the top of the cream layer.

Place the dish in the oven and bake for 20 minutes.

turn the heat down to 350 degrees F and bake for another 10 minutes.

Remove from oven, let cool 15-20 minutes before cutting and serving.