Heat the oil in a medium pot, add the onion, cumin and garlic, cook for about 2-3 minutes on medium heat.
Add the rice and mix well until the rice is coated with the onion mixture. Add the stock, bring to boil and reduce heat to low.
In the meantime, melt the butter over medium heat in a sauté pan, add the peppers, palmitos, salt and pepper. Cook for about 5 minutes, stirring often.
Add the sautéed vegetables to the rice, which should still be cooking, and continue cooking on low heat until the rice is tender.