Being that I like to cook quick (and so do you, probably), I like to dice, chop, and get everything out and measured and put aside before I even begin the cooking, so dice your onions and chop up the bell peppers. You can leave the seeds of the peppers if you'd like but make sure to de-stem them.
In a pot, heat vegetable oil over medium heat.
Add the chopped peppers, diced onions, salt, pepper, cumin, chili powder, and cayenne. Stir VERY frequently (about 1-2 minutes) and make sure that the all the spices are mixed into the vegetables.
Immediately, and in a separate pot, prepare your rice according to the package.
When rice is cooked, add it to the cooking veggies.
Add the canned tomatoes and stir frequently on medium heat.
Cook for 30-45 minutes on medium heat, stirring frequently to avoid burning the rice and so that the rice can absorb the tomato, oil, cumin, chili powder, cayenne, salt, and pepper.
If you want a variation, add small pieces of cooked hamburger meat (prepared in a separate skillet) to the mix. You can add salt, pepper, cumin, chili powder, and cayenne to that, as well, before finally adding it to the mix. If you are a brontosaurus and don't eat meat like your T-Rex friends, skip this step.
You will know the rice has absorbed everything and that everything is cooked when the rice is golden. (Note: if you believe the rice to taste too salty, gradually add just pinches of sugar until the flavor balances back out; sugar, kids, is a great equalizer -- use it wisely.).