Step 1: Preheat the Oven

Preheat the oven to 400ºF.

Step 2: Cook the Ground Beef and Onions

Heat a large frying pan over medium-high heat.

Melt the butter in the pan, then add the ground beef and chopped onions.

Season with kosher salt and black pepper, then use a spatula to break up the meat.

Cook until the beef is browned and no longer pink, about 8 minutes.

Step 3: Layer the Hotdish

Use a slotted spoon to layer about half of the beef mixture into the bottom of a 9x13-inch baking dish, draining each spoonful and discarding the excess liquid.

Add half of the vegetables over the beef, then season with more salt and pepper to taste.

Pour one can of cream of mushroom soup over the vegetables, spreading it evenly.

Layer in the remaining beef and vegetables, seasoning again as desired.

Top with the remaining can of cream of mushroom soup, spreading it evenly.

Arrange the frozen Tater Tots in a single layer over the soup in straight rows and columns, covering the entire surface.

Step 4: Bake and Serve

Transfer the baking dish to the preheated oven and bake for 45 minutes, or until the Tater Tots are golden brown and the casserole is bubbling around the edges.

Let the casserole cool slightly before serving.

Optionally, serve with ketchup on the side.

Step 5: Storing Leftovers

Let any leftovers come to room temperature before tightly covering or transferring to an airtight container.

Store in the fridge for up to 3 days.

To reheat, warm uncovered in the microwave for a few minutes until hot, or bake in a preheated 350°F oven for about 15 minutes.