The key to these muffins is letting the batter rest for 30 minutes before baking; this allows the flour to fully hydrate and the leavening agents to get a head start, which results in a taller, fluffier muffin. Starting them at a high temperature and then lowering it is another trick for getting those big, bakery-style dome tops. The batter itself is simple, using melted butter and buttermilk for a super moist and tender crumb.