Spray a 6-quart oval slow cooker with non-stick spray. Add the tater tots down in an even layer, so there isn't a high spot.
In a large skillet, set over medium high heat, brown the hamburger, onions and bell pepper. When the meat is browned, drain the fat. Add the amount of water the taco packet says to add to the meat (my packet said to add 2/3 cup). Add the taco packet, and continue cooking and stirring until the meat and the seasoning has thickened.
Pour the meat mixture over the tater tots in the slow cooker.
In a medium sized bowl add the sour cream, salt, pepper, onion powder, and half of the cheese (this is about a heaping cup of shredded cheese, save the other half to top the casserole at the end.)
Spread this sour cream cheese mixture over the meat mixture in the slow cooker.
Cover and cook on LOW for 4.5 hours, without opening the lid during the cooking time.
After the cooking time is up add the remaining cheese evenly over the casserole.
Cover and let the cheese melt, this will only take about 5-10 minutes.
To serve, top with diced tomatoes.
This recipe is very mild if you desire a more spicy version try pepper-jack cheese or replacing the bell pepper with jalapeno.Nutritional values are approximate. If you require a special diet, please use your own calculations. Values below are for 1/8 of the recipe.