Apple Texas French Toast Bake


½ cup melted salted butter
1 cup packed light brown sugar
1 whole loaf (approx 1 lb., 12 oz) fresh Texas Toast bread (not frozen. Don't use other breads.)
4 large eggs
¾ cup whole milk
¾ cup apple butter
1 tsp vanilla extract
2 granny smith apples, peeled and diced
2 TB light brown sugar, mixed with 3 tsp cinnamon
Powdered sugar for sprinkling
Maple syrup for serving