Make the caramel : in a pot on medium heat, put the sugar and some water, and leave until caramel forms. Immediately take it out of the heat and pour it into a microwavable mould.
Combine eggs, condensed milk and milk in a large bowl.
Pour the batter in the mould on top of the caramel.
Microwave for 5 minutes, full power. Open the microwave for 30 seconds and microwave again for 3 minutes. Open again for 30 seconds and cook again for 3 minutes more.
Check for doneness with a toothpick and remove from microwave. You can cook it 1 minute more if needed. Leave to cool down completely and unmould.