Allow frozen tuna to defrost for about 30 minutes, or until just soft enough to cut through
Stabilize your cutting board with a damp towel underneath, if needed. Set next to your serving platter.
Use a sharp knife to cut thin slices of tuna across the grain of the fish. Arrange them on the serving platter as you cut each piece, and season with salt and pepper as you layer the pieces.
Top the tuna with the capers, red onion, and more salt and pepper (if needed). Drizzle generously with olive oil, and sprinkle with lime zest. Add lime juice just before serving.
Serve with crusty bread or little toasts, or dressed salad greens.
If raw onions are not your thing you can try soaking them in ice water to reduce the intensity of their bite. Or you can soak them in the lime juice to give them a quick pickled effect.If your knife skills aren’t great, or you’re worried about cutting yourself, you can cut the tuna into 1 inch pieces, cover them with plastic wrap, and pound flat with a mallet.If you’re not a fan of raw fish, you can add the lime juice and let the fish sit for about 5-10 minutes. The acid in the lime juice will "cook" the fish, changing the colour, flavour, and texture.