Heat the olive oil in a large Dutch oven or heavy-bottomed pot over medium-high heat. Pat the chicken thighs dry with paper towels and season them generously with salt and black pepper.

Sear the chicken thighs skin-side down in the hot oil for 6 to 8 minutes until the skin is crispy and golden brown. Flip the chicken and cook for another 4 minutes, then transfer them to a plate and set aside.

Reduce the heat to medium, add the chopped onion to the same pot, and sauté for 5 minutes until soft and translucent. Stir in the minced garlic, kabsa spice mix, and lemon zest, cooking for about 1 minute until highly fragrant.

Stir in the tomato paste and diced tomatoes, cooking for 2 minutes while scraping up any browned bits from the bottom of the pot. Pour in the chicken broth, bring the mixture to a boil, and then return the chicken thighs and their juices back to the pot.

Cover the pot, lower the heat to a simmer, and let the chicken cook for 20 to 25 minutes until it is cooked through and tender.

Remove the chicken from the pot and keep it warm on a serving platter. Drain the soaked basmati rice and stir it directly into the bubbling, spiced tomato broth remaining in the pot.

Bring the broth back to a boil, then cover the pot with a tight-fitting lid and reduce the heat to low. Let the rice cook undisturbed for 15 minutes until all the liquid is absorbed and the grains are tender.

Turn off the heat and let the rice steam, covered, for another 5 minutes, then fluff it gently with a fork. Mound the spiced rice onto a large platter, arrange the cooked chicken on top, and garnish with toasted almonds and raisins before serving.