Preheat oven to 350 degrees.
Prepare the pan for the brownies with a nonstick pan spray or brush with melted butter. If you are using a 9 x 9 pan, I like to line with parchment so the brownies are easy to remove and cut. Set the pan aside.
Add butter and brown sugar to a microwaveable bowl. Microwave on high until the butter is melted. Make sure and mix well.
Pour mixture into medium size bowl.
Add eggs to the microwave bowl and mix. I do this just to save bowls. I don't dirty any more dishes then I absolutely have to, as I go through a lot of dishes a day! Once the eggs are mixed, add them to the butter mixture.
Add in vanilla and salt to the butter mixture as well and mix well.
Last is the dry ingredients. Add the cocoa powder, flour, and cinnamon to a fine mesh strainer over your bowl and tap until all ingredients fall into bowl. Fold until all are combined.
Now, pour into your pans and place in a preheated oven.
If you are using individual pans they take about 10-15 minutes to bake. In the larger pan, it takes about 30-45 minutes. You can use the toothpick to check.
Allow the brownies to cool for several minutes in the pan before removing. If you used the individual pans, invert over a cooling rack. You may need to help them out a little by running a knife carefully around the edges and gently prying out.
If you have used the 9x9 pan, simply lift the parchment to remove from the pan.