Toss the peaches, mango, onions, jalapeño, lime juice, and cilantro together in a large bowl. Season with salt and refrigerate for at least 1 hour before using.
Once salsa is ready, lay Tilapia on a sheet pan lined with parchment paper. Season with salt and pepper then cover with about 1/2 cup of the peach mango salsa. Place in the oven for about 18-20 minutes or until Tilapia is firm. Cooking time may vary.