Season the chicken breasts with the salt and black pepper.

Heat 1 tablespoon olive oil in a large, deep pot over medium-high heat. Add the chicken and cook for about 6–7 minutes per side, or until golden and cooked through. Transfer the chicken to a plate and set aside.

Reduce the heat to medium. Add the remaining tablespoon of olive oil, followed by the chopped onion and garlic. Sauté until the onion is soft and translucent and the garlic is fragrant.

Add the Arborio rice to the pot. Stir for 1–2 minutes so the grains are lightly toasted and coated with the oil and aromatics.

Add about 1 cup of warm chicken broth and stir. Allow the rice to gently simmer until most of the liquid has been absorbed.

Continue adding the remaining broth gradually, about 1 cup at a time, stirring regularly and allowing most of the liquid to absorb before adding more. Cook until the rice is creamy and tender with a slight bite, about 18–22 minutes.

Reduce the heat to low. Stir in the butter, Parmesan cheese, lemon zest, and lemon juice until smooth and creamy. This is what gives One-Pot Lemon Garlic Parmesan Risotto with Chicken its rich, bright flavor.

Slice the cooked chicken and return it to the pot, or arrange it over the finished risotto. Taste and adjust the salt, pepper, or lemon juice as desired.

Sprinkle with fresh parsley, if using, and serve immediately while the risotto is warm and creamy.