Preheat oven to 375°.
In a large skillet over medium heat, heat oil. Add onions and cook until soft and slightly translucent. Next add beef. When it is no longer pink, drain off some of the fat and push meat and onions to the outer edge of the skillet. Add garlic, chili powder and cumin. Stir and cook until garlic is fragrant, about 2 minutes.
Add corn, tomatoes, sour cream and 1 cup of cheese. Cook stirring regularly, until cheese is melted and sour cream is incorporated. Season with salt and pepper.
Pour mixture into a 9x13" baking pan. Top with all the tater tots and sprinkle with remaining cheese. Bake 30-35 minutes, or until cheese is melted and tater tots are hot and golden. Garnish with parsley and serve.