I bought the beef already precooked to make it easier.

Place the beef shank in a small pot to precook a bit more for 20 minutes to release its juices.

Add a tablespoon of epazote, 1 teaspoon of bay leaves, 1 teaspoon of garlic powder, and a pinch of oregano to the beef pot.

Slice the onions into rings and then cut the rings into quarters so the onion strips aren't too long.

Cook the tomatoes and onions for the Tinga. Then blend them in a blender with salt to taste.

Once the tomatoes and onions are blended, add them to the beef and stir to incorporate the tomato mixture.

Now add the onions to the beef and stir well to incorporate the onions.

Finally, serve on a plate to enjoy with a delicious tostada, sour cream, and cheese.