Preheat your oven to 400°F and line a baking sheet with parchment paper.
Lightly brush both sides of the corn tortillas with avocado oil and place them on the baking sheet.
Bake the tortillas for 4-5 minutes per side until they are golden brown and crispy.
While tortillas bake, dice the chicken breast into small bite-sized pieces.
Heat a non-stick skillet over medium-high heat and add the chicken, cumin, chili powder, garlic powder, salt, and pepper.
Sauté the chicken for 6-8 minutes until cooked through and slightly browned.
In a small pot or microwave-safe bowl, warm the black beans until heated through.
Spread the warm black beans onto the crispy tostada shells, then top with the seasoned chicken.
Garnish each tostada with sliced avocado, pico de gallo, a dollop of Greek yogurt, and fresh cilantro.
Serve immediately with a squeeze of fresh lime juice for a bright finish.