Step 1: Preheat oven to 375°F (190°C). Grease a 9x13-inch baking dish with butter or nonstick spray.
Step 2: In a large skillet over medium heat, cook ground beef and diced onion, breaking up beef, until fully browned and onion is softened (about 7-10 minutes). Drain off any excess grease.
Step 3: Add minced garlic to the skillet and cook for about 1 more minute until fragrant.
Step 4: Reduce heat slightly. Stir in cream of mushroom soup, sour cream, frozen mixed vegetables, garlic powder, pepper, and salt. Stir until well combined and heated through.
Step 5: Stir in 1 cup of the shredded cheddar cheese into the meat mixture until melted.
Step 6: Pour the mixture evenly into the prepared baking dish.
Step 7: Arrange the frozen tater tots in a single layer over the meat mixture.
Step 8: Bake uncovered in the preheated oven for 35–40 minutes, or until tots are golden brown and crispy and filling is bubbling.
Step 9: Carefully remove from oven. Sprinkle the remaining 1/2 cup shredded cheddar cheese over the tater tots.
Step 10: Return to the oven for about 5 more minutes, or until cheese is melted and bubbly.
Step 11: Let the hotdish rest for about 5-10 minutes before serving.