Peel the peaches and cut into 1-1.5 cm cubes. Put the peaches in a heat-resistant bowl, cover with sugar and top with lemon juice.
Lightly cover with plastic wrap and microwave for 4 minutes. Remove the wrap and microwave for another 4 minutes.
Keep an eye on it as you continue microwaving for 1-2 more minutes. Once it begins to bubble, it's done. Stir it a bit while it's still hot and then pour into sterilized jars.