Heat the olive oil in a large skillet over medium heat.
Add the diced onion, diced green bell pepper, minced garlic, ground beef, dry mustard, chili powder, salt, and black pepper to the skillet.
Cook the mixture, stirring frequently, until the ground beef is fully browned and broken into small pieces. Drain excess grease if necessary.
Add the uncooked long grain white rice and tomato paste to the skillet. Stir until evenly combined.
Cook the rice and tomato paste mixture for 3 minutes, stirring occasionally to prevent sticking.
Add the diced tomatoes with their juice, water, and Worcestershire sauce. Stir well to combine all ingredients.
Bring the mixture to a gentle simmer, then cover the skillet with a lid.
Reduce the heat as needed and simmer for 20 minutes, or until the rice is tender and most of the liquid has been absorbed.
Remove the lid and fluff the mixture gently with a fork.
If the mixture appears too wet, continue cooking uncovered for an additional 2 minutes, or until the excess liquid has reduced.
Sprinkle grated cheddar or Monterey Jack cheese over the top, if desired. Serve warm.