To prepare Mexican Rice: In large heavy-bottomed pan or dutch oven, heat oil until it shimmers. Add onion and saute until softened, about 2 minutes. Add rice, coating all the grains with oil. Stir often, until rice begins to brown, about 3 minutes. Add cumin, salt and garlic and stir about 1 minute until fragrant. Stir in broth and tomato sauce and bring to a boil. Cover with a tight-fitting lid and simmer about 15 minutes or until all liquid absorbs.
Assemble bowls with rice, carnitas, corn and black beans. Garnish with cheese, guacamole and salsa.