In a microwave-safe bowl, combine the garlic and jalapeño, cover with water and microwave for 1 minute at 100% power. Drain and cool completely to room temperature. Transfer to a blender jar or food processor. Pulse until everything is finely chopped, scraping down the sides to ensure everything gets caught by the blades. With the machine on, add the oil in a thin stream. If the garlic is completely cool, the oil will emulsify with the garlic, creating a thick mayonnaise-like consistency. Add the crema (or its stand-in), the lime juice or vinegar and the cilantro. Blend until everything is thoroughly incorporated. Taste and season with salt, usually a scant teaspoon.