Preheat oven to 400 degrees (200c). If you have a microwave, you can skip this step! Thinly slice the scallion, keeping the greens and whites separate. Peel, halve, and seed the cucumber, then cut the cucumber into 3-inch matchsticks. Thinly slice the radish. Halve the lime, then cut one half into wedges. Chop half the cilantro. Halve, pit, and peel the avocado, then thinly slice.

In a medium bowl, toss together the cucumber, radish, chopped cilantro, the juice of half a lime, half the sliced avocado, and 1 tablespoonolive oil. Season with salt and pepper.

Heat 1 teaspoon olive oil in a large pan over high heat. Season the tuna on all sides with salt and pepper. Add the tuna to the pan and sear 1-2 minutes per side, until golden brown on the outside but still rare on the inside.

Meanwhile, wrap the tortillas in tin foil and place in the oven to warm for 3-5 minutes. Alternately, wrap them in a damp paper towel and microwave on high for 30 seconds.

Cut the tuna into 1/2-inch cubes. Toss the tuna in medium bowl with the scallion whites, 1 1/2 tablespoons mayonnaise, and half the sriracha (or less, to taste). Season with salt and pepper

Assemble the tacos: place the spicy tuna inside each tortilla, then top with a few slices avocado, a bit of the slaw, a sprig of cilantro, and the scallion greens. Serve lime wedges and remaining slaw to the side. Enjoy!