Unfortunately, there is no way to fix burnt caramel sauce. You will know that the caramel is overcooked if it is a dark brown or black color, smells burnt, or has swirls of smoke that might sting your eyes. To avoid this, make sure you are stirring the sauce consistently so it does not burn on the bottom of the pot, and keep an eye on the color of the caramel! If your sauce does end up burning, you will need to start again.