Directions :
Dredge the cubed meat in flour, coating well.
In a heavy, deep-sided skillet or Dutch oven, add the oil and heat over medium heat. Add the cubed meat and brown thoroughly, stirring often.
While the meat is browning, in a small saute pan, toast the comino seeds and then add them to the molcajete (mortar and pestal). Use the same pan to toast the serrano pepper.
In a molcajete that already has the comino, add the garlic, and black peppercorns. Grind into a paste. Add 1/2 cup of water and stir, this is to make sure you remove all the paste from the molcajete and set aside.
Once the meat is browned, add the garlic, comino and peppercorn paste and liquid from molcajete to the pot. Add the salt, paprika, oregano, chili powder, onion, tomatoes, cilantro, and serrano to the pot and saute for 3 to 4 minutes.
Add beef broth, bring to a boil and then reduce heat to low, cover, and cook for 1 1/2 hours, or until the beef is tender and the mixture has cooked down to a thick sauce. Stir every 20 minutes.
Enjoy!