Bring salted water to a boil in a pot. Rinse the millet in a sieve under running water and cook it for about 15 minutes. Then drain the millet in a sieve and let it cool.
Wash and finely chop the parsley while the millet is cooking. Peel and finely chop the garlic. Peel the onion and cut it into thin strips. Then wash the tomatoes and dice them.
Wash the lemon thoroughly. Grate the zest and squeeze out the juice.
In a bowl, combine the olive oil with lemon juice and zest, and salt. Then add the tomatoes, parsley, chopped garlic, and onion and mix in the millet.
Finally, season with freshly ground black pepper and serve with walnuts or unsalted pistachios, if desired.