Prepare a cast iron skillet with oil, or an 8x8 pan with non stick spray.
In a large mixing bowl whisk the flour, baking powder, baking soda, salt, and cinnamon together and set aside.
Using a handheld or stand mixer fitted with paddle attachment, beat the butter on high speed until smooth and creamy. Add both sugars to the butter and beat for two minutes. Scrape down the sides of the bowl and add the eggs and vanilla, beating on medium speed until combined. Beat in the mashed banana.
With the mixer running on low speed add the dry ingredients in three additions alternating with the milk and mixing just until combined.
Stir in the toffee baking bits.
Spread batter evenly into prepared skillet or pan.
Bake for 25-35 minutes, or until the top is light golden brown and a toothpick inserted in the center comes out clean.