Cook the rice in salted water according to your usual method until fully cooked. Drain if needed and set aside.
Melt 2 tablespoons of the butter in a large pan over medium heat.
Add the onion, garlic, scallion, thyme, and pimento peppers, if using. Sauté until the onion begins to soften.
Add the carrots and red and green bell peppers. Sauté for about 5 minutes, until the vegetables are softened but still have a little bite.
Add half of the cooked rice and mix with the vegetables. Add the remaining rice and mix until the vegetables are evenly distributed throughout.
Add the remaining 1 tablespoon butter and black pepper. Taste and add salt if needed.
If the rice seems dry, add a little more butter or coconut oil and mix well.
Stir in the chopped cilantro and serve.