Preheat the broiler. Line a baking sheet with foil. Toss the tomatoes, lettuce, red onion, cilantro and lime juice in a medium bowl; season with salt and pepper. Set aside.
Toss the chicken with the chili powder and a generous pinch each of salt and pepper. Heat the olive oil in a large skillet over high heat. Working in batches, add the chicken and cook, flipping, until well browned but not fully cooked through, about 2 minutes. Transfer to the prepared baking sheet and top evenly with the cheese. Broil until the cheese melts and the chicken is cooked through, about 1 minute.
Combine the yogurt and 1 tablespoon water in a small bowl. Stir in the lime zest and a pinch of salt.
Divide the salad among plates and top with the chicken and tortilla chips. Drizzle with the lime yogurt and sprinkle with cilantro and pepper.
Photograph by Ryan Dausch