Ingredients:
Dressing:

• 1/4 cup fresh lime juice
• 1/2 cup fresh cilantro, chopped
• 1 teaspoon sugar
• 1 tablespoon chili powder
• 1/4 teaspoon ground cumin
• 1/2 teaspoon salt
• 1/4 teaspoon black pepper
• 1/2 cup olive oil

Beef:

• 1 medium onion, chopped
• 3 garlic cloves, finely chopped
• 1 to 2 fresh Serrano chilies, finely chopped
• 1 tablespoon chili powder
• 2 teaspoons ground cumin
• 2 tablespoons olive oil
• 1 1/2 pounds ground chuck
• 1 (8-ounce) can tomato sauce
• 1/2 teaspoon salt
• 1/4 teaspoon black pepper

Salad:

• 1 (1/2-pound) firm-ripe avocado
• 1 head iceberg lettuce, thinly sliced (8 cups)
• 1 large tomato (1/2-pound), chopped
• 1/4 pound extra-sharp cheddar (1 1/2 cups), coarsely grated
• 1 (19-ounce) can black beans, drained and rinsed
• 1 (6-ounce) can sliced pitted black olives, drained

Preparation:
Whisk together lime juice, cilantro, sugar, chili powder, cumin, salt, and pepper, then add oil in a stream, whisking until emulsified.

Cook onion, garlic, chilies to taste, chili powder, and cumin in oil in a 12-inch heavy skillet over moderate heat, stirring occasionally, until onion is well softened, about 6 minutes. Add beef and cook, stirring occasionally and breaking up lumps, until meat is no longer pink, about 5 minutes, and then spoon off any excess fat from skillet. Add tomato sauce, salt, and pepper to beef and cook, stirring, until slightly thickened, about 3 minutes. Remove from heat.

Peel and pit avocado, then cut into 1/2 inch pieces.

Spread lettuce over bottom of a shallow 4-quart dish. Spoon beef mixture evenly over lettuce and continue making layers with tomatoes, cheese, beans, avocado, and olives. Drizzle dressing over salad.