Line a muffin tin with 10 tulip style paper muffin liners.
Preheat oven to 425 degrees F.
In a large bowl, whisk together the flour, baking powder, cinnamon and salt. Pour in the 3 cups of cereal and stir to combine.
In a separate mixing bowl, whisk together the buttermilk, melted butter, egg, sugar and vanilla extract until very smooth.
Pour the wet mixture into the dry and gently stir until combined and no streaks of flour remain. Allow to rest for about 10 minutes or until the batter puffs up.
Give it one more stir to combine. Use a 1/4-cup capacity muffin scoop to fill the 10 liners with batter.
Bake the muffins at 425 degrees F for 7 minutes. Without opening the door, reduce the heat to 350 degrees F and bake for 5 minutes more.
Rotate the muffin tin front to back. Bake 10-12 more minutes at 350 degrees F. A total baking time of 22-24 minutes. Muffins are done when they spring back when lightly touched with a finger.