Heat oil in a medium saucepan and add the onions. Cook on medium heat till they are soft. Add the garlic, and jalapeno and stir 2 minutes. Then add cumin, oregano, tomatoes, and salt. Cook the same on medium heat for about 3 minutes.

Wipe the portabellos with a paper towel. Then using a small spoon, gently scrape out the dark gills. Using a small, sharp knife, remove the stem. Brush a little oil all over the mushrooms.

Heat a skillet on medium high, and cook the mushrooms, gill side down, in a single layer for 2 minutes. Then flip the mushrooms and cook the other side another minute or till cooked through. While the second side is cooking, sprinkle salt and half the oregano over the mushrooms cavities.

In the same skillet, heat a little more oil, add the zucchini and remaining oregano. Saute on high heat for about 2 minutes or till the zucchini is tender but still a little crunchy, and not mushy. Sprinkle salt, and the cheese.

Dissolve the bouillon cubes in warm water and set aside. Sauté the onions in butter or olive oil in a medium saucepan. When the onions are soft, add the Achiote powder and rice. Stir on low heat for a minute.

Pour in the bullion water, and bring to a boil. Reduce heat to a low, cover the pan, and let the rice simmer for 10 minutes or till the rice is cooked, but the grains are still separate, and not mushy. Fluff rice with a fork. Garnish with cilantro.

Spread ranchero sauce on a platter. Arrange the mushrooms, gill and stem side up, over the sauce. Spoon a little zucchini and cheese into the mushroom cavities. Serve the yellow rice on the side, along with sour cream (optional), extra cheese and extra chopped cilantro.