You will need:
1. Mix a paste of baking soda and water in a small dish. It should be the consistency of toothpaste.
2. Spread the paste over the burnt area and allow it to set for about 12 minutes. Do not allow to sit too long or it will dry out. Really it will.
3. Pour a little lemon juice (bottled worked for me!) over the paste and let it fizz to help release tougher stains.
4. After 12 minutes, gently scrub the area with a soft cloth or plastic scrubber. Do not use anything abrasive or it will scratch the surface. Found that out the hard way one time.
5. Repeat as necessary until food is gone. GONE I tell you! So happy right now.
6. Clean off surface with a wet cloth or paper towel.
Source: How to Clean Stuff