Prep the asparagus and onions before setting the water to boil for the ravioli. Add salt to the water for flavoring.
In your largest skillet, heat the olive oil and red pepper flakes.
Saute the onions until they soften and change color about 10 minutes.
Reduce the heat and add the asparagus to the onions and stir to coat in the oil. Saute until crisp tender, about 5 minutes, add a little water from the pasta if needed to prevent sticking.
Meanwhile, cook the ravioli as directed when the water comes to a boil.
Reduce the heat on the asparagus and add a couple tablespoons of parmesan cheese, the lemon juice and zest. Stir to coat.
Transfer the ravioli to the skillet using a slotted spoon.
Gently combine the ravioli with the asparagus and sauce. Add more pasta water if needed.
Transfer to a platter, season as desired and garnish with more cheese.