Position an oven rack in the top third of the oven and preheat to 425 degrees F. Set a wire rack over a baking sheet and spray generously with cooking spray.
Use your hands to mix the ground beef, taco seasoning and 1/2 teaspoon salt in a medium bowl until just combined. Drop heaping tablespoons of the meat mixture onto the rack (about 16 total), then use your hands to roll the portioned meat into balls. Press a tortilla chip into the top of each meatball, making sure that the meat goes mostly up the sides of the chip (be careful not to break the chips). Put 1 cheese cube in the middle of each chip.
Bake, rotating the baking sheet once halfway, until the meat is just cooked through and the cheese is melted, about 8 minutes. Transfer the bites to a large platter, top with a dollop of sour cream and sprinkle with the lettuce and tomato. Serve with hot sauce.
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