Beef Tacos

1 pound lean chuck roast
Vegetable oil
1 small onion, chopped
1 garlic clove, minced
1/4 teaspoon cuminseed
1/2 teaspoon ground coriander
1 tablespoon chili powder
1/2 cup water
8 corn tortillas
Shredded lettuce
1 avocado
Sour cream

Chop meat into 1/4-inch pieces. Heat a little oil, then saut