Preheat your oven to 400°F (200°C).
Season the chicken breast with half of the sea salt, black pepper, and fresh thyme.
Place the chicken on a parchment-lined baking sheet and roast for 20-25 minutes, or until the internal temperature reaches 165°F.
While the chicken is roasting, heat the olive oil in a small saucepan over medium heat.
Add the finely diced yellow onion and minced garlic to the saucepan, sautéing for 3-4 minutes until the onion is translucent and fragrant.
Stir in the dry brown rice and toast for 1 minute, then pour in the chicken broth.
Bring the broth to a boil, then reduce the heat to low, cover, and simmer for 35-40 minutes until all liquid is absorbed and the rice is tender.
Once the rice is cooked, remove from heat and stir in the baby spinach, fresh parsley, lemon juice, lemon zest, and the remaining salt and pepper.
Cover the pot for 2 minutes to allow the spinach to wilt from the residual heat of the rice.
Slice the roasted chicken breast and serve it over the fluffy lemon-herb rice pilaf.