Heat oven to 350°F; butter a 9-by-13-inch baking dish.

Spread pineapple and its juice over bottom. Distribute peaches on top; sprinkle with brown sugar.

Cover fruit evenly with dry cake mix; do not stir.

Scatter pecans over mix; slowly drizzle melted butter over entire surface.

Bake 45 to 50 minutes until deep golden with no powdery patches and fruit bubbling at edges.

Rest 25 minutes before serving to let filling settle.