Preheat your oven to the temperature specified on the tater tot package. Line a baking sheet with aluminum foil and lightly grease.
Spread the tater tots in a single layer on the baking sheet. Bake them according to the package instructions until they are golden brown and crispy.
While the tater tots are baking, mix 1 cup of Greek yogurt with your ranch seasoning mix in a small bowl.
Once the tater tots are done, remove them from the oven and switch the oven to broil. Sprinkle the cheddar cheese over the tater tots. Broil for 3 to 4 minutes, or until the cheese is melted.