Beef and black bean lettuce cups

Ingredients

• 2 tablespoons dry sherry
• 1 1/2 tablespoon black bean sauce
• 1 teaspoon sugar
• 2 tablespoons vegetable oil
• 500 grams budget beef rump steak
• 1 large white onion, cut into thin wedges
• 1 large carrot, peeled, halved, thinly sliced diagonally
• 1 medium red capsicum, thinly sliced
• 1 medium zucchini, trimmed, halved, thinly sliced diagonally
• 8 iceberg lettuce leaves, to serve