Slice the chicken breast into thin, uniform strips.
Heat the olive oil in a large skillet over medium-high heat.
Add the chicken strips, sliced bell peppers, and red onions to the skillet.
Sprinkle the chili powder, ground cumin, smoked paprika, sea salt, and black pepper over the chicken and vegetables.
Sauté for 7 to 9 minutes, stirring frequently, until the chicken is fully cooked and the vegetables are tender-crisp.
Place the corn tostada shells on a flat surface or serving plate.
Evenly divide the chicken and pepper mixture between the two tostada shells.
Top each tostada with a dollop of plain Greek yogurt, slices of fresh avocado, and a sprinkle of cilantro.
Squeeze the fresh lime juice over the top and serve immediately.