Preheat the oven to 425°F and lightly grease a 9x13 baking dish.
In a large skillet over medium-high heat, brown the ground beef and chopped onion until the beef is no longer pink, about 6 to 8 minutes. Drain excess oil.
Add 1 cup of Thousand Island dressing, chopped pickles, mayonnaise, ketchup, mustard, onion powder, smoked paprika, kosher salt, and black pepper to the skillet; stir until fully combined.
Spread the meat mixture evenly into the prepared baking dish.
Sprinkle shredded cheddar cheese evenly over the meat mixture.
Arrange the frozen tater tots in a single layer on top of the cheese, ensuring not to overcrowd for crispiness.
Bake uncovered for 25 to 30 minutes, or until the tater tots are golden brown.
Let the casserole rest a few minutes before spreading shredded lettuce evenly over the tots.
Drizzle the remaining 1/4 cup of Thousand Island dressing and sprinkle sesame seeds on top. Serve warm.