In a large skillet, over medium heat, cook the ground beef or turkey until browned. Drain any excess fat.
Stir in the taco seasoning and add ¼ cup of water. Cook for another 2-3 minutes until the mixture thickens slightly.
In a large mixing bowl, combine the cooked meat, black beans, corn, half of the cheddar cheese, and diced tomatoes (reserve some for garnish). Mix until well combined.
Arrange the taco shells upright in a baking dish. Spoon the meat and bean mixture evenly into each taco shell.
Top with the remaining cheddar cheese and sprinkle the chopped jalapeño on top (if using).
Cover the baking dish with aluminum foil and bake for 15 minutes. Remove the foil and bake for an additional 10-15 minutes or until the cheese is bubbly and golden.
Remove from the oven and let cool for a few minutes. Top with shredded lettuce, remaining diced tomatoes, and garnish with fresh cilantro.
Serve with sour cream on the side.
Notes
Arrange the tacos on a platter, garnish with extra cheese and cilantro, and serve with lime wedges for an added zest!