Wash and quarter the quinces and remove the cores. Dice the pulp and cook with 500 ml water for 20-25 minutes. Peel the apples, remove the core and also dice. Mix with the lemon juice.
Puree the cooked quince with the cooking liquid and the apple pieces. Then mix the whole thing with the preserving sugar and bring to the boil. Let it boil for 4 minutes while stirring, then pour into glasses and close immediately.