To start, preheat the oven to 350⁰F (180⁰C). Line a 9x9-inch baking dish with non-stick baking paper, or grease it with some butter or cooking spray. If you are making a double recipe, use a 9x13-inch baking dish. Set it aside.
Mix together the softened butter and brown sugar in a large bowl. Beat the ingredients together very well until you have a uniform, creamy, lump-free mixture.
Add the egg and mix it in well.
Next, add the sifted flour, salt, baking powder, and cinnamon. Again, mix the ingredients well until you have a uniform dough.
Press this dough-like mixture into the lined baking dish. Make sure it is shaped into an evenly thick layer.
Then, in a small separate mixing bowl, whisk together the sugar and cinnamon.
Sprinkle your homemade cinnamon sugar over the dough. Evenly distribute the mixture over the whole area.
Finally, bake the churro bar cake for 25 minutes or until the center is no longer gooey.
Once baked, remove the bars from the oven and leave them to cool at room temperature. Cut them into pieces and serve them within a couple of days.