Grease a 13 x 9 pan and set aside.
In heavy medium pot, melt Butter with Coffee Powder over low heat. Remove from heat.
Whisk in Brown Sugar, Vanilla, and Eggs until combined.
Using a wooden spoon, mix in Flour, Baking Powder, Salt and the Cinnamon (if using) until just mixed.
Spread into greased pan, smoothing the batter into the corners.
Bake 25-30 minutes or until a toothpick near the edge of the pan is clean.
Cool on wire rack. If using the glaze, be sure to cool COMPLETELY before topping with the glaze.