- Combine red onion, Italian parsley, mint, garlic, 1/2 cup olive oil, and salt & pepper in a small bowl. Zest the lemon into the mixture, then squeeze the juice into the bowl. Mix well and set aside.
- Add 2 tbsp olive oil to a heated, heavy wide skillet and add riced cauliflower. Season with salt & pepper.
- Saute on medium heat for about 12 minutes, stirring frequently so that all of the riced cauliflower pieces begin to turn a golden brown color.
- Meanwhile, heat another heavy skillet and add remaining 2 tbsp olive oil. When pan is pretty hot, lay tuna steaks inside and let cook on medium-high heat for about 3 minutes, until you see the bottom layer cooked and the very center still pink, then flip and cook another 2 - 3 minutes, until the other side is cooked and center is still rare enough for your liking.
- Remove from pan and transfer to a cutting board, then slice 1/2 inch thick slices perpendicular to the grain.
- Serve a few slices of tuna drizzled with generous spoonfuls of the green relish and a side of the riced cauliflower.
- If you can not find riced cauliflower at your local grocery store, you can remove stems, then rough chop a whole head, and place in a food processor for a few quick pulses.