Preheat oven to 425°F. Arrange tater tots in a single layer on a large rimmed baking sheet. Bake for 25-30 minutes until golden brown and crispy.
While tots are baking, cook ground beef in a large skillet over medium-high heat, breaking it up with a spoon, until browned and cooked through, about 6-8 minutes.
Drain excess fat from beef, then stir in taco seasoning according to package directions. Keep warm.
Remove crispy tater tots from oven. Sprinkle half of the cheddar cheese over the tots, then add the seasoned ground beef evenly.
Top with remaining cheddar cheese, Mexican cheese blend, and sliced jalapeños. Return to oven for 8-10 minutes until cheese is melted and bubbly.
Remove from oven and immediately top with diced tomatoes, red onion, green onions, and cilantro.
Serve immediately with sour cream and avocado slices on the side. Provide forks and napkins for easy eating.
Notes
For extra crispy tots, bake 5 minutes longer than package directions before adding toppings. Add wet toppings only after baking to prevent sogginess. Leftovers can be reheated in the oven at 375°F for 10-12 minutes.