Slice the chicken breast into thin, bite-sized strips for even cooking and maximum spice coverage.
In a medium bowl, whisk together the ground cumin, ground coriander, ground turmeric, garlic powder, sea salt, and black pepper.
Toss the chicken strips in the spice blend until every piece is thoroughly coated.
Heat the olive oil in a large cast-iron skillet over medium-high heat until shimmering.
Add the chicken to the skillet in a single layer, searing for 3-4 minutes per side until deeply browned and cooked through.
While the chicken cooks, dice the cucumber and halve the cherry tomatoes, then toss them with lemon juice in a small bowl.
Scoop the warm, cooked brown rice into a serving bowl.
Arrange the spiced chicken and the fresh cucumber-tomato salad over the rice.
Finish with a dollop of creamy Greek yogurt on top before serving.