Slice the chicken breast into thin, even strips and place them in a bowl.
Season the chicken with chili powder, ground cumin, garlic powder, sea salt, and black pepper, tossing to coat thoroughly.
Heat the olive oil in a large skillet over medium-high heat until shimmering.
Add the seasoned chicken to the skillet and sauté for 5-7 minutes until browned and cooked through, then remove from the pan and set aside.
In the same skillet, add the sliced bell peppers and red onion, cooking for 4-5 minutes until they are tender-crisp and have slight charred edges.
While the vegetables cook, warm the black beans in a small saucepan over low heat or in a microwave-safe bowl.
Lay the corn tostadas on a clean surface and spread an even layer of warm black beans onto each one.
Top the beans with the sautéed chicken and the pepper and onion mixture.
Drizzle the fresh lime juice over the tostadas and serve immediately.