The amount of salt you need will depend on how much salt is in your chicken broth. 1/2 tsp of salt is a good starting point. After you add everything together, taste the liquid. It should taste a little salty, but after the rice cooks, it will balance out.
Heat oil in a large saucepan over medium heat and add onions. Cook, stirring constantly, until starting to get color. Add rice for the last 2 min. While rice is cooking, sprinkle with salt, cumin, onion, and garlic powder.
Stir in tomato sauce and chicken broth; bring to a boil. Reduce heat to low, cover and simmer for 20 to 25 minutes.
Turn off heat, and wait 10 minutes without opening.
To serve fluff with a fork. I like to garnish with cilantro, lime wedges, and diced white onions