In the crock, add onions, chipotle peppers (with all the adobo sauce), zest and juice from all the citrus and beef broth. Stir to combine. Place chuck roast in middle of crock.
Combine remaining seasonings in a small bowl. Then pour evenly over the top of the chuck roast. Secure lid and let cook for 8 hours on Low (or 4 hours on high).
Remove meat from crock to a bowl. Use a fork to shred meat. Then add about a cup of the liquid and toss with shredded meat.
Using a grill pan, gently grill each tortilla (use a little cooking spray if needed).
To build a taco - start with grilled tortilla, add generous amount of shredded beef, then a couple of spoonfuls of peach salsa. Last sprinkle with cojita cheese.