Zucchini stuffed with tuna with light gratin

Ingredients: 4 medium zucchini; 2 cans tuna in water, drained; 1/4 white onion, finely chopped; 1 tomato, diced; 1/4 cup yellow corn; 1 tsp salt; 1/4 tsp pepper; 1/2 cup shredded Oaxaca or mozzarella cheese; 1 tbsp vegetable oil. Preparation: Prepare the zucchini: 1. Cut lengthwise and remove some of the center with a spoon. 2. Boil for 5 minutes in salted water. 3. Drain and set aside. Filling: 1. In a pan with oil, sauté onion for 3 minutes. 2. Add tomato (3 min). 3. Incorporate tuna, corn, salt, and pepper (2 min). Baking: 1. Fill the zucchini. 2. Add cheese on top. 3. Bake at 190 °C for 15 minutes, until gratinéed.