In a large bowl, mix 2 quarts of cold water with 1/2 cup of Kosher salt to create your brine. Submerge the chicken thighs in the solution and refrigerate for 30 to 60 minutes.

Preheat your oven to 400°F (200°C). Spread the rinsed plum tomatoes on a baking sheet and roast them for about 30 minutes.

Remove the chicken from the brine and pat it dry with paper towels. In a deep skillet, heat 2-3 tablespoons of olive oil over medium-high heat. Add the chicken thighs and brown them for about 5-6 minutes on each side until golden.

In a blender, combine the roasted tomatoes, 1/2 small onion, 2 garlic cloves, and 1 jalapeño. Blend on high until smooth and well combined.

In the same skillet, add 2 cups of uncooked rice, stirring for about 3-4 minutes until it becomes opaque. Pour in the blended tomato sauce and mix well.

Add 3 cups of stock to the skillet along with 1 tablespoon of Mexican oregano, 1/4 teaspoon of cumin, salt, and black pepper to taste. Stir everything together, adjusting seasoning as needed.

Carefully return the browned chicken to the skillet, arranging it on top of the rice mixture. Bring to a gentle boil, then cover and let it simmer for about 20-25 minutes.

Once cooked, remove the skillet from heat and let it sit, still covered, for a few minutes before serving. Garnish with cilantro if desired.