Place beef and quartered onion in a large pot; pour in enough water to cover. Bring to a boil. Stir in salt. Cook for about 2 1/2 hours.

Add tomatoes to the boiling beef; cook until tender, about 10 minutes. Remove from heat.

Transfer tomatoes to a blender using a slotted spoon. Add chipotle peppers and 1 1/2 cups cooking liquid from the pot. Blend well and set aside.

Remove beef chunks from the pot, reserving remaining cooking liquid. Shred beef with 2 forks; discard any excess fat.

Heat olive oil over medium heat in a medium pot. Saute sliced onion until softened, about 5 minutes. Add shredded beef and saute for about 5 minutes. Pour in blended chipotle sauce. Add more of the reserved cooking liquid, if needed, to reach the desired consistency. Bring to a boil. Stir in chicken bouillon and simmer for about 5 minutes more.