Preheat oven to 350 degrees F (175 degrees C). Line 2 baking sheets with parchment paper or silicone mat.

Spread Cheddar cheese into four 6-inch circles, placed 2 inches apart.

Bake in the preheated oven until cheese melts and is lightly brown, 6 to 8 minutes.

Cool for 2 to 3 minutes before lifting with a spatula. Place over wooden spoon handle wrapped in aluminum foil balanced over 2 cups/cans. Let taco shells cool completely, about 10 minutes.

Cook beef in a skillet over medium-high heat until browned, stirring often to separate meat, about 7 minutes. Season with taco seasoning, salt, and pepper; cook for 1 minute more.

Divide beef mixture among cheese taco shells. Top with avocado, lettuce, Cheddar cheese, and tomatoes.