Preheat oven to 400°F (200°C). In a large skillet, heat oil over medium-high heat. Cook onions, stirring often, until tender and golden, about 7 min. Add chicken and cook until golden on the outside, about 5 min. Remove from heat and stir in butter chicken sauce.
Spread tomato sauce packet over pizza crust. Spread chicken mixture over pizza and sprinkle with cheese. Bake on middle rack of oven until cheese is melted and bubbly, about 12 min. Garnish with green onions and slice into wedges.