Prepare the Meat Filling:
In a skillet over medium heat, cook the ground beef (or turkey) until browned, breaking it apart with a spatula.
Add diced onion and cook for another 2-3 minutes until softened.
Stir in taco seasoning and water, and simmer for 5 minutes, until the mixture thickens. Remove from heat and set aside.
Preheat the Oven:
Preheat your oven to 375°F (190°C).
Prepare the Taco Bites:
Lightly grease the muffin tin with cooking spray or olive oil.
Use a round cookie cutter or a cup to cut small circles from the tortillas (about 3-4 inches in diameter) to fit into the muffin cups.
Press each tortilla circle into the muffin tin to form little taco shells.
Assemble the Taco Bites:
Spoon the cooked meat mixture into each tortilla cup, filling each one about halfway.
Sprinkle shredded cheese over the top of the meat.
Bake the Taco Bites:
Bake in the preheated oven for 10-12 minutes, or until the tortillas are golden and the cheese is melted and bubbly.