Heat the oil in a large skillet over medium-high heat. Season the chicken with the 1/2 tsp salt and 1/4 tsp pepper. Brown the chicken on both sides, then transfer the chicken to a plate.
Add the onion, bell pepper, garlic, and cumin to the pan and cook, stirring occasionally, until the vegetables are softened, about 5 minutes. Meanwhile, in a small saucepan, bring the beer, chicken broth, tomato sauce, salt, and 1 cup of water to a simmer.
Stir a good pinch of saffron into the vegetable mixture and cook for another minute. Add the rice and stir until all of the rice is coated in oil. Transfer the rice mixture to an 8×8-inch glass or ceramic baking dish, spreading it in an even layer. Carefully pour the broth mixture over the rice. Arrange the chicken on top. Cover the dish tightly with foil.
Bake, covered, for 30 minutes. Taste the rice for doneness, and check that the chicken is at least 180F inside—set the dish back in the oven for a few more minutes if necessary. Enjoy!