Preheat your oven to 450°F. Lay the corn tortillas flat on a rimmed baking sheet and brush both sides with oil until they look lightly glossy. Bake for 10 minutes, flipping them at the 5-minute mark and rotating the pan for even browning. The tortillas are ready when they turn golden brown and feel crispy to the touch.

While the tortillas bake, place a medium saucepan over medium heat. Add the shredded chicken, salsa, taco seasoning, drained corn, and black beans. Stir everything together and cook for about 5 minutes until the mixture is heated through and steaming with gentle bubbling around the edges.

Remove the crispy tortillas from the oven and carefully add about 1/2 cup of the hot chicken mixture to each one, spreading it out slightly but leaving a small border around the edges. Top each tostada with 1/4 cup of shredded cheese, distributing it evenly over the chicken mixture.

Return the loaded tostadas to the oven and bake for 5 more minutes until the cheese is completely melted and bubbly. Watch them closely during this final bake to prevent burning.

Remove from the oven and immediately top with fresh cilantro and diced tomatoes. Serve right away with lime wedges on the side for squeezing over the top.