Rinse the quinoa thoroughly under cold water, then combine with 0.5 cup of water in a small pot; bring to a boil, then reduce heat and simmer covered for 15 minutes until fluffy.
Season the chicken breast evenly on both sides with sea salt, black pepper, and dried oregano.
Heat the olive oil in a non-stick skillet over medium-high heat and sear the chicken for 5-7 minutes per side until golden brown and cooked through.
While the chicken cooks, steam the broccolini for 4-5 minutes until it reaches a tender-crisp texture and bright green color.
Slice the cherry tomatoes in half, pit and chop the kalamata olives, and mince the garlic clove.
Remove the chicken from the pan and set aside; in the same pan, quickly sauté the garlic, tomatoes, and olives with the lemon juice for 2 minutes to create the topping.
Fluff the quinoa with a fork and plate it alongside the steamed broccolini and chicken fillet.
Spoon the warm olive and tomato mixture over the chicken and serve immediately.