1. Melt butter in a nonstick skillet over medium-high heat; add onion, and sauté 5 minutes or until tender. Cool slightly.
2. Stir together cooked onion, ground turkey, and next 3 ingredients in a large bowl until well blended. Shape into an 8- x 5-inch loaf; place on a lightly greased rack in an aluminum foil-lined broiler pan.
3. Pour chili sauce evenly over meatloaf.
4. Bake at 350° for 1 hour and 20 minutes to 1 hour and 30 minutes or until done. Let stand 10 minutes before serving.