This is an extremely satisfying dish, with richly flavored rice and browned calamari that will surprise even those who think they don't like squid. The same recipe can also be made with peeled shrimp instead of calamari.
If squid is not already cleaned, prepare it by pulling off the heads and drawing out the soft innards. Remove the quill, and cut the tentacles just above the eyes. Discard the eyes, heads, innards, and quills and wash the rest carefully in a cold water bath with lemon. Peel away and discard the colored outer skin. Drain and pat dry.
Slice the bodies into thin rings or — if the squid are large ones — into matchstick pieces.
In a dry frying pan over high heat, pan-fry squid until it has released all its liquid. Pour this liquid off and heat until the pan is dry again. Set aside the calamari.
Finely dice the onions and caramelize them in 3 tablespoons olive oil adding ½ teaspoon salt and stirring. If necessary splash them with a little water and continue until they are golden brown. Take care not to burn them. Set aside 1/2 of the caramelized onions. To the remaining 1/2, add cumin and filfil mat’houn and stir. Then, add the squid and lemon juice. Stir over high heat until all lemon juice evaporates and squid browns slightly. Remove from heat.
Place the other 1/2 of the caramelized onions in a small pot for rice over medium-high heat. Add 1 tablespoon olive oil. When this is hot, add 1/2the rice. Stir continuously until the rice has browned noticeably. Add the other 1/2 of the rice, mix, and add 2 cups of water. Add a pinch of salt and, if desired, a few crushed pearls of mastic.
When water boils, lower the heat and allow to simmer slowly until rice is al dente. Add a small part of the calamari and mix into the rice. Remove from heat and allow rice to repose for a few minutes.
Spread rice into a serving plate and cover with the remaining calamari.