Grilled tuna with zucchini and tomatoes

Heat a non-stick frying pan over medium-high heat. Spray with oil and add onion. Cook stirring for 3 minutes or until soft. Add garlic and cook for a further minute. Add zucchini and stir for 2 minutes, then add tomatoes, stock amd balsamic vinegar. Season to taste with salt and pepper. Reduce heat to low and simmer for 5 minutes or until zucchini is tender. Meanwhile heat a grill pan over high heat. Spray tuna with oil and season with salt and pepper. Grill for 1 minute each side or until cooked to your liking. Serve with zucchini and tomato.