- In a pot of salted boiling water, cook the pasta until al dente. Drain and toss with a little oil.
- Meanwhile, place the green onion in a small bowl and cover with cold water. Drain when ready to serve.
- In a large bowl, using a fork, mash 1 avocado with the lemon zest and half of the lemon juice. Add the mayonnaise and mix well. Season with salt and pepper. Stir in the cooled pasta.
- Thinly slice the other avocado and drizzle with the remaining lemon juice.
- Serve the pasta in bowls. Garnish with the tuna, bell pepper, arugula, green onion and slices of avocado.