If using chicken breasts, place them between two sheets of plastic wrap or in a zip-top bag and pound to an even thickness of about 3/4 inch using a meat mallet or heavy skillet. This helps them cook evenly so the thin end does not dry out before the thick center is done.

In a bowl or zip-top bag, whisk together 2 tablespoons of the olive oil, the lemon juice, garlic, oregano, salt, and pepper. Add the chicken and turn to coat. Let it marinate at room temperature for 15 minutes, or cover and refrigerate for up to 24 hours.

While the chicken marinates, cook your rice or farro according to the package directions. Season the cooked grain with a small pinch of salt and a drizzle of olive oil, then set aside covered to stay warm.

Heat the remaining 1 tablespoon of olive oil in a large skillet over medium-high heat until the oil shimmers. Remove the chicken from the marinade, letting the excess drip off, and place it in the skillet. Cook without moving it for 5 to 6 minutes until a golden crust forms on the bottom.

Flip the chicken and cook another 5 to 7 minutes, or until an instant-read thermometer inserted into the thickest part reads 165 degrees F. If the pan gets too dark, lower the heat slightly. Transfer the chicken to a cutting board and let it rest for 5 minutes before slicing.

Divide the rice or farro among four bowls. Top each bowl with sliced chicken, cherry tomatoes, cucumber, and red onion. Spoon a generous dollop of tzatziki over the top and finish with fresh parsley. Serve immediately.