Tater Tot Breakfast Casserole

cooking spray
1/2 lb breakfast sausage
1 small onion, diced
1/2 C milk
5 large eggs
1/2 tsp onion powder
1/2 tsp salt
1/4 tsp garlic powder
1/4 tsp ground black pepper
1-12 oz pkg shredded cheddar cheese, divided
1-16 oz pkg frozen bite-size potato nuggets (such as tater tots)

Preheat the oven to 350 degree. Lightly spray a two-quart baking dish with cooking spray. Heat a large skillet over medium-high heat. Cook and stir sausage and onion in the hot skillet until sausage is browned and crumbly, five to seven minutes. Drain and cool. Meanwhile, whisk milk, eggs, onion powder, salt, garlic powder, and pepper together in a bowl. Spread sausage mixture over the bottom of the prepared baking dish. Pour egg mixture over the top. Layer with 1/2 of the cheddar cheese and all the potato nuggets. Cover with aluminum foil. Neatly arranged tater tots in a baking dish, partially covered. Bake in the preheated oven for 40 minutes. Remove the foil and sprinkle with the remaining cheese. Bake until melted for about 20 minutes more. Remove from the oven and let stand briefly before serving.