Heat olive oil in a large skillet over medium-high heat. Place the beef in the hot skillet, and brown it quickly on all sides.
Transfer the roast to a slow cooker and top it with the chopped onion. Season with peppers, chili powder, cayenne pepper, hot sauce, cumin and garlic powder. Add enough water to cover 1/3 of the roast and the bouillon cube.
Cover, and cook on High for 8 hours, checking to make sure there is always at least a small amount of liquid in the bottom of the cooker.
Transfer the roast to a bowl and shred it using two forks.
Spoon off the fat in the crock pot, and remove a majority of the onions/peppers via a slotted spoon. Return the shredded meat to crock pot juice and cook on low for 1 1/2 hours. This is important; it allows the spiced juice that has formed to really get in that meat.
When you replace the beef add 1/2 tsp. of additional cumin and 1 tsp. of paprika. Best served in tacos or sandwiches.
