Rinse the tongue. Start out by rinsing the beef tongue really well to make sure that you do away with as many impurities as possible.
Place lengua in cooker. Now you can place it in the slow cooker. Remove the skin from the onion, cut it in half and put it on top of it evenly distribute the garlic, salt, pepper, and the bay leaf.
Cook the tongue. Cover the tongue with water and then slow cook it on low for 8 continuous hours or until the tongue feels tender when you piece it with a knife.
Remove the skin. At this point, use the paring knife to remove and throw away the skin. Then you can cut it up into small cube-like pieces.
Slow cook the tongue. Return it to the slow cooker and bring down the heat level to just warm.
Serve. Allow everyone to served themselves on top of the tortillas and adding the amount of each topping, radishes, cilantro, and lime, that they want.