In a small bowl, combine cumin, paprika, chili powder, onion powder, oregano, salt, and pepper. Divide spice mixture in half and rub half of it all over chicken legs. Set remaining half aside.
Heat a large skillet over medium-high heat. Add vegetable oil and swirl to coat pan. Place spice-rubbed chicken legs in a single layer in pan and sear on all sides, turning occasionally until golden-brown (about 3-4 minutes). Transfer chicken to a plate and set aside.
In same skillet over medium-high heat, sauté onion in drippings until translucent. Reduce heat to medium and add garlic, tomato paste, rice and remaining spice mixture to pan and cook 2-3 minutes.
Pour chicken broth into pan and bring to a simmer. Reduce heat to medium-low and nestle chicken back into pan. Cover pan and let Spanish rice simmer 20-25 minutes or until rice is tender and chicken registers 165F. Season rice with additional salt and pepper to taste if needed.
Just before serving, squeeze fresh lime juice over Spanish rice and sprinkle with cilantro. Serve hot and enjoy!