Place a skillet over medium heat and cook the ground beef, breaking it apart with a spoon until fully browned and no pink remains.

Drain any excess fat from the skillet so the filling stays rich but not greasy.

Stir the taco seasoning into the cooked beef until evenly coated and aromatic.

Add the diced tomatoes and green chiles along with their juices, then simmer the mixture for about 5 minutes until slightly thickened.

Transfer the warm taco mixture to a large bowl and allow it to cool slightly.

Add the shredded cheddar cheese and ranch dressing to the bowl, then stir until everything is evenly combined and creamy.

Arrange the frozen phyllo tart shells on the prepared baking sheet.

Spoon the taco filling into each shell, filling them generously but not overflowing.

Bake the filled shells in the preheated oven until the cheese melts and the filling becomes hot and bubbly.

Remove from the oven and allow the bites to cool slightly before serving so the filling sets inside the crispy shells.