Preheat the oven to 400°. In a skillet, melt 2 tablespoons of the butter. Add the peaches and cook over high heat, stirring occasionally, until just softened, 8 minutes. Add 4 tablespoons of the brown sugar and the lemon juice and cook until the peaches are lightly caramelized, about 5 minutes; scrape into a 1½-quart baking dish.