Preheat oven to 350°F (175°C).
In a skillet over medium heat, cook the ground beef until no longer pink. Drain any excess fat.
Add taco seasoning and the can of diced tomatoes with green chiles. Stir well and cook for about 5 minutes until thickened.
In a large bowl, mix the shredded cheddar cheese and ranch dressing. Add the cooked beef mixture and stir until evenly combined.
Spoon the mixture into the frozen phyllo tart shells, filling each one generously.
Arrange filled shells on a baking sheet and bake for 8–10 minutes, or 10–13 minutes if the shells are still frozen, until golden and bubbly.
Let cool slightly before serving warm.
