Blanch the peaches in boiling water in the large saucepan for 45 seconds. Refresh in cold water, peel, and slice into the small saucepan. Sprinkle with the lemon juice and add sugar. (The amount of sugar required will vary with the sweetness of the peaches.) Bring to a boil in the saucepan over high heat, stirring. Reduce heat and simmer for 15 minutes. Rub through the strainer with the back of a wooden spoon or with a pestle. Refrigerate if not used immediately.