Gratin de carottes et thon

​Ingredients 

6 cups finely grated carrot (560 g) 
250 g cherry tomatoes, halved 
2 medium onions, diced 
2 cups cheddar (185 g) 
2 cans tuna packed in oil (200 g each)
1 can tuna packed in water (200 g)
1 can chopped tomates (425 mL)