Place flour, brown sugar, and butter for the topping in a small food processor. Pulse until all ingredients are combined, and mixture looks like coarse crumbs.
Evenly sprinkle topping over unbaked bread.
Bake at 400 degrees for 45-60 minutes, until the top is brown and a toothpick inserted in the center tests clean. Check bread after 40 minutes, and loosely cover with aluminum foil if the top is getting too brown.