1. 1. Preheat the oven to 350°F (180°C).

2. 2. Cook the egg noodles according to package instructions. Drain and set aside.

3. 3. In a large mixing bowl, combine the cooked egg noodles, rotel tomatoes, condensed cream of mushroom soup, diced onion, and cajun seasoning. Mix well to combine.

4. 4. Transfer the mixture to a baking dish and spread it evenly.

5. 5. Bake in the preheated oven for 25-30 minutes, or until bubbly and heated through.

6. 6. Serve hot and enjoy!