Step 1

Rub roast with 2 tablespoons olive oil all over.

Step 2

In a small mixing bowl combine chili powder and next 6 ingredients and sprinkle evenly over entire roast.

Step 3

Arrange onion in the bottom of a crock pot or slow cooker and place seasoned roast on top. Add garlic, water and vinegar.

Step 4

Cook on low for 8-9 hours until tender and begins to fall apart easily.

Step 5

Remove from crock pot and using two forks pull on opposing sides to shred. Taste and adjust salt and pepper seasoning if needed.

Step 6

In a small mixing bowl add sour cream, avocados, lime juice and salt and pepper and mash to blend well.

Step 7

Layer shredded beef in tortillas followed by shredded cheese and next 6 ingredients (as desired).

Step 8

Top with avocado crema and serve.