Stir-Fried Eggs with Tomatoes

Name: Stir-Fried Eggs with Tomatoes (Fan Qie Chao Dan 番茄炒蛋)
Cuisine: Chinese
Ingredients: 2 eggs; 2 ripe tomatoes, similar in volume to the eggs; ½ tsp potato flour mixed with 2 tsp water (optional); Salt; 4 tbsp cooking oil; ½ tsp caster sugar