For the pea rice with tuna, bring water to a boil and sprinkle in rice. Let the rice steam on low heat for about 15 minutes. Finely chop the garlic clove, heat the oil and fry the garlic in it until hot.
Add the peas and tuna and sauté briefly. Add the rice and season with salt, pepper and oregano. Arrange the pea rice with tuna and serve.