Finely chop a small red onion and place it in a bowl. Squeeze the juice of 2 limes over the onions and sprinkle with kosher salt. Mix well and let sit for at least 10 minutes.

Bring a large pot of salted water to a rolling boil. Add 1/2 pound of cavatappi and cook until al dente, about 8 to 10 minutes. Drain and cool the pasta.

Prepare the shrimp by bringing a separate pot of water to a boil. Add 1 pound of shrimp and cook for exactly 2 minutes. Transfer to an ice bath for 2 minutes.

In a large mixing bowl, combine the chilled pasta, pickled onions, cooked shrimp, diced red bell pepper, halved cherry tomatoes, and chopped cilantro. Season with Old Bay and olive oil, and toss gently.