In a large skillet or Dutch oven, over medium heat, add the oil and the chorizo. Using a spatula, break the chorizo apart until it looks crumbled. Sauté the meat for about 5 minutes, until the chorizo releases some of its fat. Add the red and yellow onions to the meat, and sauté for another 8 – 9 minutes, until the onions begin to caramelize. Add in the garlic and oregano, seasoning the mixture with salt, and cook for another minute. Deglaze the pan with the beer, using the spatula to scrape any fond from the bottom of the pan. Reduce the beer until it’s almost evaporated, just lightly coating the onions and chorizo, about 5 minutes.
Remove from the heat and keep warm for the torta.