Spread sugar over bottom of a heavy skillet, preferably one that is not cast iron or one without a nonstick interior. It is easier to seethe color change in a stainless steel skillet.
Cook over medium low heat until the sugar begins to melt. Stir very gently so the sugar melts evenly. When the sugar is melted, cook, without stirring, until the caramel is dark reddish-brown (about 10-15 minutes). Swirl pan gently to check for color; watch closely as the color changes quickly.