1. Heat a large nonstick skillet over high. Rub 2 tablespoons of the lemon juice over the chicken. Sprinkle chicken evenly with salt, pepper, paprika, and thyme.
2. Spray pan with cooking spray. Sear chicken until brown but not cooked through, about 2 minutes per side. Remove chicken from pan to a plate.
3. In the same pan, lower heat to medium and add onion. Sauté until slightly browed, about 4-5 minutes.
4. Mix in rice, garlic, lemon zest, thyme, and salt. Stir and sauté until rice is coated with mixture and slightly translucent, about 3-4 more minutes.
5. Add chicken broth and spinach. Bring to a boil, scraping the brown bits from the bottom of the pan. When liquid is boiling, lay chicken on top of the liquid/rice mixture.
6. Cover the skillet, lower heat to medium-low, and simmer for 15-20 minutes, or until the rice is just cooked through.
7. Remove pan from heat. Move chicken to plate again and stir the lemon juice and grated parmesan into the rice until everything is melted and the rice is creamy.
8. Sprinkle rice with chopped parsley, if desired. Serve one piece of chicken with 1 cup of rice mixture.