Preheat the oven to 400 degrees. Brown the ground beef in a skillet or other heavy bottomed pan over medium heat. Break the meat into bite-sized pieces and continue cooking until no pink remains.
Add the onions to the skillet with the beef and cook for 3-4 minutes until fragrant.
Pour in the diced tomatoes and juice.
Add the corn, beans, chili powder, cumin, garlic powder, salt, and pepper to the pan and mix to combine.
Stir in the sour cream.
Scrape the ingredients into an 8x8-inch baking dish that’s been prepared with pan spray. Smooth the filling into an even layer.
Place the tater tots on top of the casserole dish, covering the filling as evenly as possible.
Sprinkle the cheese on top of the tater tots.
Place the dish into the oven and bake for 25-30 minutes until the filling is bubbling at the sides and tater tots are browned and crispy. Serve warm.