Lamb and tomato stir-fry

Ingredients

• 2 tablespoons vegetable oil
• 500 grams lamb leg steaks, sliced
• 1 red onion, thinly sliced
• 2 cloves garlic, crushed
• 1 tablespoon grated ginger
• 1 red capsicum, thinly sliced
• 1 bunch broccolini, sliced
• 4 large roma tomatoes, roughly chopped
• steamed rice to serve
• Sauce
• 1/4 cup soy sauce
• 1/4 cup white wine vinegar
• 2 tablespoons fish sauce
• 2 tablespoons caster sugar
• 2 teaspoons cornflour