You may have. Is it an amber color or has it become dark red-brown? It happens very quickly
I always use the safer and more tedious system of adding water to the sugar, (1/3 cup water to 1 cup sugar) boiling covered until dissolved, and then boiling uncovered and undisturbed until all the water boils off and it caramelizes. That way the syrup heats evenly and caramelizes all at the same time. (You would then add the water in the recipe to make a syrup) If takes longer, but with Maya's method you can have some scorched parts.
If it's only "kind of" bitter you could still use it in the cake--there are so many other ingredients.