In a large skillet over medium-high heat, combine the broth, pesto, heavy cream, and lemon juice; stir until well blended and the pesto melts into the liquid.
Bring the sauce to a gentle simmer, then add the refrigerated ravioli, stirring to coat each piece in the sauce.
Cover the skillet and reduce heat to medium-low; cook for 5 minutes with the lid on so the ravioli heat through and release a bit of starch.
Uncover and stir; if the sauce is still too thin, continue cooking uncovered for 1–2 more minutes until it reaches your desired thickness.
Add the packed baby spinach, stir, then cover briefly for 1–2 minutes until the spinach wilts.
Taste and season with salt and pepper as needed, then serve with freshly grated Parmesan on top if using.