| Preheat oven to 350°F |
| Grease a 9x13-in baking dish |
| 12 oz spaghetti, broken in half | boil until just tender, 8 to 10 min, drain | toss together, spread in the dish | sprinkle over | bake 350°F until bubbly, 20 to 25 min |
| 2 Tbsp butter | cook until soft, 5 min | stir over low heat until the cheese melts | stir in |
| 1 medium onion, chopped |
| 1 can (10 3/4 oz) condensed cream of mushroom soup |
| 1 can (10 oz) diced tomatoes with green chiles (Rotel), undrained |
| 8 oz Velveeta, cubed |
| 1 cup chicken broth |
| 3 cups cooked chicken, shredded |
| 1/2 tsp black pepper |
| 1 cup cheddar cheese, shredded |