1. Preheat oven to 350°.
2. Drain pineapple, reserving 3 tablespoons juice. Chop pineapple to measure 3 cups.
3. Combine chopped pineapple, reserved juice, and peach slices in an 11 x 7inch baking dish coated with cooking spray. Stir butter into cake mix until smooth. Spread batter over fruit; coat with cooking spray.
4. Bake at 350° for 38 minutes or until golden and bubbly. Serve warm with frozen yogurt. Sprinkle each serving with 1 tablespoon pecans, if desired.