Smash the garlic cloves with the side of a knife to release the flavor and aroma. Add smashed cloves, salt and the whole half of an onion to the water. Peel the orange and add the peel to the water, then squeeze in the juice.
Slowly add the beef tongue to the boiling water. Cover the pot and simmer for 4-5 hours. The beef tongue is ready when a knife is easily inserted into the middle of the flesh with little resistance.
Remove the tongue from the pot and discard the water. Allow the tongue to cool 10-15 minutes before handling.
Peel the skin away, if necessary using a small knife to remove any stubborn bits. Discard the tongue skin.
Slice the tongue into 1/4" slices, and cut away a wedge of the darker "under tongue" section. (See post above for more info). Season the slices well on both sides with Meatchelada seasoning.
Heat a grill for high heat grilling, about 500f. Alternatively, you can also do this sear step in a skillet on the stove.
Grill the tongue pieces, flipping frequently. The tongue is already cooked at this stage, you are just looking to develop a seared crust on the outside. As the fat begins to render the caramelization will speed up, so be careful of flare ups.
Once the desired color is achieved, removed from the grill and serve immediately.