Preheat a skillet over medium heat.
In a bowl, mix the cooked ground beef with taco seasoning, cooked rice, and diced tomatoes.
Lay one tortilla flat and spread half of the mixture in the center. Top with half of the shredded cheddar cheese, then drizzle with nacho cheese sauce and sour cream.
Fold the sides of the tortilla in, then roll it up tightly from the bottom to enclose the filling.
Repeat with the second tortilla and remaining ingredients.
Melt 1/2 tablespoon of butter in the skillet. Place one burrito seam-side down in the skillet and cook for about 3-4 minutes until golden brown.
While the first burrito cooks, sprinkle some shredded cheddar cheese on top. Carefully flip the burrito and cook for another 3-4 minutes until the other side is golden and the cheese is melted.
Remove the burrito from the skillet and repeat with the second burrito, adding the remaining butter.
Slice the burritos in half and serve with shredded lettuce on the side.