Pillowy cinnamon focaccia built on an apple cider dough, layered with diced apples and spiced sugar, then baked hot and finished with a crunchy cinnamon-sugar crust.
Do 4 rounds of stretch and folds, resting 30 minutes between each round. To do a round, grab one edge of the dough with a wet hand, stretch it up, and fold it over the center; rotate the bowl a quarter turn and repeat until you have gone all the way around.
After the final round, cover and let rise 1 hour, until doubled and bubbly.
Mix the granulated sugar, brown sugar, cinnamon, nutmeg, cardamom, and salt in a small bowl. Butter a 9x13" (23x33 cm) pan generously with the 4 tbsp melted butter.
Add the dough to the pan and gently stretch it to the edges.
Scatter the diced apples over the top and sprinkle with one third of the cinnamon sugar.
Fold the dough in half, rotate it, return it to the pan, and gently stretch it back out to the edges.
Cover and proof 2 hours, until very puffy and jiggly.
Cider vs. juice. Both apple cider and apple juice work. Cider is a little less sweet, which balances the cinnamon sugar better; juice makes a sweeter loaf. Use whichever you have.
Liquid temperature matters. Cider hotter than 115°F (46°C) will kill the yeast. If it does not foam in 10 minutes, the yeast is dead — start over.
Apple choice. Firm, tart apples (Granny Smith, Honeycrisp, Braeburn) hold their shape and cut the sweetness. Soft apples turn to mush in the bake.
Dimple all the way down. Pressing only the surface gives you a domed bread instead of focaccia. Push your fingers to the bottom of the pan.
The final sprinkle must be immediate. Cinnamon sugar added to the hot, buttery top melts into a thin crackly shell; added after it cools, it just falls off.