Mix all the marinade ingredients together, then pour the mixture over the cleaned chicken breasts. Set them aside for at least 2-3 hours.

Rinse the quinoa thoroughly in a fine-mesh sieve, several times in hot water. Then, place it in a pot, cover it with water, and add ½ teaspoon of salt. Cook covered, over low heat for about 20-25 minutes or until soft. If necessary, gradually add small amounts of water. By the end of cooking, the quinoa should be soft and have absorbed all the water.

Prepare the salad: cut the cucumbers into smaller pieces (you can peel them if you prefer), halve the cherry tomatoes, thinly slice the red onion, and slice the olives. Mix the prepared vegetables together, drizzle with olive oil, and sprinkle with a pinch of oregano and crumbled feta cheese.

Prepare the tzatziki: grate the cucumbers on a coarse grater (you can peel them if you prefer), then add the grated garlic, Greek yoghurt, salt, and black pepper.

Heat a small amount of olive oil in a grill pan. Remove any excess marinade from the chicken, then briefly fry the chicken over fairly high heat on each side. Reduce the heat to low/medium and continue frying for about 5-7 minutes on each side. After this time, cut into the thickest part of one of the breasts. If the meat is still raw inside, cook for a few more minutes until it is completely cooked through. Remove the meat from the pan and set it aside for a while, then cut it into slices.

Place the salad, quinoa, and chicken slices on plates. Serve with tzatziki sauce. Enjoy your meal!