Start by bringing a large pot of salted water to a boil. Add the spaghetti and cook according to package instructions until al dente. Reserve 1 cup of pasta water, then drain the spaghetti and set aside.
While the pasta is cooking, heat 2 tablespoons of olive oil in a large skillet over medium heat. Season the chicken breasts with 1/2 teaspoon of salt and 1/4 teaspoon of pepper. Add the chicken to the skillet and cook for about 6-7 minutes on each side, or until fully cooked and golden brown. Remove the chicken from the skillet and let it rest for a few minutes before slicing it into strips.
In the same skillet, add minced garlic and cook for about 30 seconds until fragrant. Then, add the ricotta cheese, grated parmesan cheese, lemon juice, lemon zest, oregano, and the remaining salt and pepper. Stir to combine and create a creamy sauce. If the sauce is too thick, gradually add reserved pasta water until you reach your desired consistency.
Add the cooked spaghetti to the skillet with the creamy sauce, tossing to coat the pasta evenly. Stir in the chopped spinach and sliced chicken, allowing the spinach to wilt slightly. Cook for an additional 2-3 minutes to heat everything through.
Plate the creamy lemon chicken pasta and garnish with extra parmesan cheese and a sprinkle of lemon zest if desired. Enjoy this delightful dish warm, and watch it disappear from your table!