Start by cutting the chicken breasts into small, bite-sized pieces.

In a mixing bowl, combine the chili powder, cumin, garlic powder, salt, and pepper. Toss the chicken pieces in this spice mix until they are well coated.

Heat olive oil in a skillet over medium-high heat.

Add the seasoned chicken to the hot skillet. Cook for about 5-7 minutes, stirring occasionally, until the chicken is cooked through and no longer pink.

While the chicken cooks, warm the tortillas in a separate pan or microwave.

Fill each tortilla with the cooked chicken and top with diced tomatoes, shredded lettuce, and cheese.

If desired, add a dollop of sour cream and sprinkle fresh cilantro on top.

Arrange the tacos on a platter and serve immediately.