In an interview with Eating Well, Rachael Ray shares her views on traditional mayo-based tuna salad and makes a convincing argument for why you should skip the mayo.
Ray points out that mayonnaise obscures the umami-rich flavor of canned tuna. Instead, she opts to "only dress tuna with lemon juice and olive oil so you can taste the product."
Whereas a creamy, buttery mayonnaise will mask the fishiness of tuna, Ray believes that olive oil and lemon juice are complementary flavors that showcase tuna's distinct flavor.
In addition to adding copious amounts of olive oil to tuna, you also "need to dress the salad [or tomato] underneath it ... and add more olive oil to enhance that flavor."