First, brown the ground beef in your skillet over medium heat, breaking it up as it cooks until no pink remains. Drain any excess grease, then return the beef to the pan. Add the taco seasoning, undrained can of diced tomatoes with chilies, and the water. Stir everything together and simmer until the liquid is mostly absorbed.
Once the beef mixture is nicely simmered, stir in the cubed Velveeta cheese, cover the skillet and let the cheese melt into the meat for about 5 minutes. If you prefer a slightly thicker filling that holds its shape better, sprinkle in the cornmeal and mix thoroughly.
Preheat your oven to 350°F (about 175°C). Line your rimmed baking sheet with nonstick foil. Arrange the scoop chips cup-side up on the sheet. Spoon approximately ½ teaspoon of the beef mixture into each chip cup, then top with about ½ teaspoon of shredded cheddar cheese. Bake in the oven for 6-7 minutes or until the cheddar has fully melted.
Remove the baked bites from the oven. Immediately top each with a small dollop of sour cream, a sprinkle of shredded lettuce, and some diced tomatoes. Serve warm for best taste and texture.