Wash the pan with a mild liquid dish soap and nylon scrubbing sponge. Remove as much of the food residue as possible, but do not worry about scrubbing too hard at this stage.
Rinse out the pan and sprinkle a thin layer of baking soda into the bottom. Add up to 1/4 cup of white vinegar. The vinegar and baking soda will bubble up as they react.
Add 1 quart of hot tap water to the pan and place it in the oven at 325 degrees Fahrenheit for at least 30 minutes.
Remove the pan from the oven and allow it to cool and soak in the water, vinegar and baking soda overnight.
Wash the pan as usual and dry it thoroughly before putting it away.