Measure 2 tablespoons lemon juice into a large non-reactive bowl. Add the fruit to the bowl and toss to coat.
Melt the butter over medium heat in a non-reactive roasting pan or rimmed baking sheet. Cook until it stops foaming and turns light brown. Add the rosemary, bay leaves, vinegar, remaining lemon juice, and brown sugar. Bring to a boil, stir well until the sugar has melted, and simmer until slightly reduced.
Season the cut fruit with a pinch of salt and pepper and pour into the roasting pan. Stir well until evenly coated.
Spread the fruit into a single layer and place in the oven. Let cook slowly about 6 hours, turning the pieces over every hour for at least the first 3 hours. To test whether the fruit is ready, remove a piece after 2 hours and let cool for a few minutes. Taste to see if the flavor is intense enough for your palate. Do not let the fruit get as dry as a fruit leather. It should still be moist and flexible. Remove any pieces that are done before the rest. Remove from the oven, let cool completely, and store in a tightly sealed container.
Refrigerate, if not consumed within 2 days. Let come to room temperature or warm gently before serving, if refrigerated. The fruit will keep a week or more in the refrigerator.
Cook's Note: Oven-drying is a technique for intensifying flavor. If the fruit is watery, it may take up to 8 hours to dry. If the fruit is at its peak, ripe, and firm, it may take far less time.