Preheat oven to 375°F and spray a 9x13 baking dish with nonstick cooking spray.
In a skillet or saucepan over medium-high heat, brown the ground beef, chopped onion, and minced garlic until beef is fully cooked, about 5-7 minutes. Drain excess fat.
Spread the cooked beef mixture evenly in the bottom of the prepared baking dish.
In a mixing bowl, whisk together cream of mushroom soup, sour cream, milk, kosher salt, onion powder, and black pepper until smooth.
Stir in 1/2 cup of shredded cheddar cheese and drained green beans, mixing gently to avoid crushing the beans.
Pour the soup mixture evenly over the ground beef layer in the baking dish.
Sprinkle the remaining 1 1/2 cups shredded cheddar cheese over the soup layer.
Arrange the Tater Tots in a single layer on top.
Bake for 45-50 minutes until Tater Tots are golden brown and sauce is bubbling. Serve hot.