Melt the butter in a medium, heavy-bottomed saucepan over medium-low heat.
Add the rice, onion and green pepper, and saute until the rice is slightly browned and the vegetables are softened, 8 to 10 minutes. Stir in the tomatoes, pimiento, salt, cayenne and hot sauce. Bring to a boil, cover and reduce the heat to low. Simmer for 20 minutes, then fluff with a fork. If the rice is tender but too soupy, cook uncovered for another 5 minutes. If the rice is dry but not yet tender, add 1/2 cup water, cover and continue cooking for another 5 minutes, or until the rice is done.