Preheat the oven to 400°F (200°C).
In a large skillet over medium heat, brown the ground beef or turkey until fully cooked. Drain any excess fat.
Add the chopped onion and minced garlic to the skillet, cooking until softened, about 3-4 minutes.
Stir in the drained diced tomatoes, black beans, corn, chili powder, cumin, salt, and pepper. Cook for an additional 5 minutes until heated through.
Transfer the mixture to the 9x13-inch casserole dish, spreading it evenly across the bottom.
Arrange the frozen tater tots in an even layer on top of the meat and vegetable mixture. If using, sprinkle the dairy-free cheese shreds over the tater tots.
Place the casserole dish in the preheated oven and bake for 25-30 minutes, or until the tater tots are golden brown and crispy.
Once done, take the casserole out of the oven and let it cool for a few minutes before serving.