optional garnish: chopped cilantro and lime wedges
In a large freezer bag (or bowl), add chicken, 1 tablespoon of olive oil, vinegar, onion powder, chili powder, paprika, salt, oregano and cumin. Seal the bag and shake up to completely coat the chicken with the marinade. Refrigerate for at least 30 minutes, up to overnight.
Heat a large oven-safe saute pan/deep skillet over medium-high heat. Add the 1 tablespoon of olive oil. Add half of the chicken thighs to the pan and cook for 2 minutes per side, or until chicken is no longer pink on the outside. Transfer the chicken onto a plate and cook the remaining chicken the same way.
Preheat oven to 350°F. In the same saute pan/skillet, add the remaining 1/2 tablespoon of olive oil. (If the skillet is already very greasy and has enough oil to cover the bottom of the pan due to cooking the chicken, you can omit this last addition of oil.)
Add the rice and saute for 10 minutes, stirring occasionally, until the rice begins to brown slightly. At this point, some grains of rice may even pop. That's okay. This step adds some nuttiness and more depth of flavor to the rice.
Add in the onions and minced garlic. Saute for about 30 seconds until fragrant. Add in the water, tomato paste and a generous pinch of salt. Stir together to mix until the tomato paste has fully dissolved.
Cover the saute pan with a lid or foil, place it in the oven and bake for 15 minutes. Remove it from oven, place the partially cooked chicken thighs on top of the rice, cover and cook for another 15 minutes.
Remove the lid or foil and bake for another 5 minutes uncovered. Check the temperature of the chicken thighs to make sure they're cooked through using a meat thermometer like this one or by slicing into one.
Remove the pan from the oven and let cool slightly before serving. Garnish with diced cilantro and fresh lime juice, if desired.