Prepare a batch of same-day focaccia dough following recipe instructions up until transferring to tray
While dough is proofing, brown the salted butter
Mix browned butter with light brown sugar, cinnamon, and vanilla extract
Peel and finely dice 2-3 apples
Line parchment on tray with 2 tablespoons melted salted butter
Transfer dough to 9x13 inch tray and gently stretch to edges
Mix ⅓ of diced apples with half of cinnamon filling and spread over dough
Fold up dough as shown in video, flip over, and cover to finish proofing for 1-1.5 hours at room temperature
Preheat oven to 215°C/420°F with rack in lowest position
Warm cinnamon sugar butter to drizzling consistency
Mix remaining ⅔ diced apples with remaining cinnamon filling, spread over dough, and dimple in
Bake for 23-25 minutes
While baking, whisk together powdered sugar, milk, vanilla extract, and cinnamon for glaze
Drizzle glaze over focaccia once out of oven and brush on top, sides, and bottom
Transfer to cooling rack for 15 minutes for glaze to harden
