Activate the yeast. In a small bowl, combine warm water (about 110℉) and granulated sugar. Sprinkle the active dry yeast over the top and let it sit for 10-15 minutes until it becomes foamy.

Mix the dough. In a large mixing bowl, whisk together the flour and salt. Then, pour in the activated yeast mixture along with the olive oil. Stir until the dough forms a stick dough ball. Rub the surface of the dough lightly with olive oil.

First rise. Cover the bowl with a damp tea towel or plastic wrap and place it in the refrigerator for at least 12 hours.

Grease a 9x13-inch baking pan and line with parchment paper. Pour 2 tablespoons of melted butter into the center of the pan. Gently deflate the dough and place it into the buttered pan. Cover and let it rise for 1.5 to 2 hours in a warm spot.

Make the brown butter. In a small saucepan, melt 1/2 cup butter over medium heat. Stir until it turns golden-amber. Remove from heat immediately and let cool for 10 minutes.

Make the cinnamon topping. Add the brown sugar and cinnamon to the browned butter, mixing until dissolved.

Preheat the oven to 450℉. Press deep dimples all over the dough surface. Drizzle the cinnamon-butter evenly over the dimpled dough.

Bake for 20-25 minutes until golden brown. Let cool for 10 minutes in the pan, then transfer to a cooling rack.

Combine powdered sugar, milk, and vanilla extract in a bowl, mixing until smooth. Drizzle over the warm focaccia, slice into squares, and enjoy!