Cook the pasta as per the package directions for al dente pasta.
Drain and rinse gently under cold water until the pasta feels cold to the touch.
Drain well.
Place the drained pasta in a very large mixing bowl.
Break up the tuna, and add it to the pasta along with the chopped vegetables.
Toss gently with a fork.
Add the mayonnaise gradually, tossing with the fork as you go. You don’t want the salad too moist, but you do want the mayonnaise to cover all the pasta, vegetables and tuna generously. Add more mayonnaise if you need to.
Gently fold in the lemon juice.
Taste the salad and add salt, pepper and/or more lemon juice, if desired.
Transfer the salad into a serving bowl or individual Tupperware style containers.
Chill before serving if time allows.
Refrigerate leftovers for up to 24 hours.