Preheat the oven to 375° and have ready a greased 9x13" casserole dish.
Add to ground beef, chili powder, cumin, salt, pepper, and garlic powder to a large sauté pan over medium-high heat. Break apart the meat, blending in the spices and cook for 8-10 minutes, stirring often.
Use a slotted spoon to transfer the beef to a bowl and set aside. Turn off the heat and carefully, spoon out all but a thin layer of grease and discard. Resume medium-high heat setting, add the diced onion and sauté 3-4 minutes, until softened.
Add the beef back into the pan, along with crushed tomatoes, beef broth, and corn. Bring to a simmer.
In a small bowl, mix together cornstarch with 2 tablespoons of water, and stir into the beef mixture. Simmer 3-4 minutes until thickened. Turn off the heat and stir in sour cream and 1 cup of Cheddar cheese.
Add half of the tater tots to the prepared casserole dish and pour over the beef mixture. Stir to combine. Top with the remaining tater tots and bake for 25 minutes, uncovered.
Add the Cheddar cheese and bake for 10 minutes more. Allow to cool slightly, serve, and enjoy.