At about 3½ – 4 minutes mark, sugar will be melted and rapidly bubbling. Soon after that it will turn pale golden, then increasingly amber. Once the browning starts, it will continue to do so very rapidly, so keep a very close eye. My caramel reached the required dark amber color around the 5 minute mark. Stop the microwave and using oven mitts carefully remove from the oven. Alternatively caramel can be made on the stove using David Lebovitz’s method.