Preheat oven to 350 °F. Melt margarine in saucepan over low heat. Stir in brown sugar until dissolved. Cool slightly. Beat in egg and vanilla. Stir in flour, baking powder, and salt. Spread batter into greased 9x9 baking pan. Bake 20 - 25 minutes.
Notes
These make thin, chewy bars. The recipe can be doubled and baked in a 9x13 pan. Increase baking time to about 40 minutes. I've also added about a cup of chocolate chips to a double batch of this - they all sank to the bottom, but it was good nonetheless. :-)
This works fine with margarine or butter (if milk is okay for you), but I have not tried it with egg replacer. These have not worked egg-free with anything I have tried.
Butter and Margarine: Butter is a dairy product made from cow’s milk. Margarine typically contains milk or soy, but there are milk-free and soy-free versions available.
Corn Substitutions: Corn is a common ingredient in products. Starch, modified food starch, dextrin and maltodextrin can be from corn. Consult with your physician to find out which corn derivatives you need to avoid. Many corn-free options are available in the US. Find out more about corn substitutions.
Egg Substitutions: There are many egg-free products and foods available to make your recipes free of eggs. Find out more about egg substitutions.
Gluten: Gluten is a protein found in specific grains (wheat, spelt, kamut, barley, rye). Other grains are naturally gluten-free but may have cross-contact with gluten-containing grains. Look for certified gluten-free products if you need to avoid gluten. Find out more about wheat and gluten substitutions.