Soak the tuna steaks in water with lemon and a small pinch of salt for some 15 minutes
While the tuna is soaking, chop the onion and the garlic
After 15 minutes, take the tuna out of the water and cut into large pieces
Add the onion, and the garlic to brown over medium heat. We want it golden but not burned, so you will need to stir often. If you are not a fan of garlic, once it's golden, you can remove it. Otherwise, you can leave it.
Once they are of a light brown color, add the tuna and stir often for some 2 to 3 minutes over medium to high fire.
When the tuna has slightly changed color but is still quite raw, add the wine and increase the fire until it completely evaporates.
Once the wine is fully evaporated, lower the fire again and add the peeled tomatoes. You can add them whole and roughly smash them with the spoon in the pan.
Add the olives and the capers roughly chopped or even whole, leave the fire at medium, put the lid, and let cook for 5 to 10 minutes until the tomato is thickened. Keep in mind that the tuna cooks fast and by now it's already lightly cooked, so check often not to overcook it.
Near the end, when it's almost done, add the chopped parsley, a few leaves of fresh basil, and a bit of mint.