*Sofrito refers to a sauce or culinary base involving small diced garlic, onions and other savories cooked or sautéed slowly using butter or olive oil.
To make this sofrito start with a large sauté pan, and melt butter over medium heat. Then add onions and salt, and cooked them slowly, stirring often, until they are soft and light golden, about 1 hour. Add the garlic and cook until soft, 8 to 10 minutes. Remove from the heat and add the cilantro, lime zest and lime juice. Taste and adjust seasoning with salt. Let cool.