Steps
1. Preheat oven to 350°F (175°C).
2. In a skillet, melt butter over medium heat. Add onions and sauté until translucent.
3. Add beans, corn, and tomatoes. Cook for 5 minutes.
4. Transfer the mixture to a baking dish.
5. Bake for 20 minutes or until bubbly and golden.
6. Serve hot and enjoy!