Bring a large pot of well-salted water to a boil. Cook the pasta to al dente according to the package directions. Drain and rinse under cold water.Let the pasta sit for 10 minutes to drain off excess water.
Meanwhile, place a rack at the top of the oven. Toss the corn and zucchini with olive oil and 1/2 teaspoon of kosher salt and spread them out on a large baking sheet.
Broil the corn and zucchini for 5 to 6 minutes stirring halfway through. Pull them from the oven when they have a bit of char on them. Caution: Keep an eye on them to prevent burning.
In a large mixing bowl, whisk together the mayo, lemon juice, sugar, 1 teaspoon of kosher salt, and pepper until well combined.
Add the pasta, roasted corn and zucchini, tomatoes, and red onion. Toss until everything is well combined.
Serve immediately or cover and chill for several hours or overnight before serving.
Notes
Store in an airtight container for up to 5 days.Note: the sauce will start to absorb into the pasta if stored longer than 1 day. If you expect to have leftovers for several days, I suggest making a bit more sauce to mix with the pasta salad just before serving.