If necessary, thaw the frozen fish in the refrigerator overnight. If using fresh, skip this step.
Place the thawed or fresh fish in the freezer for about 10-15 minutes while preparing ingredients. This helps make the fish easier to slice.
Juice the lemons or yuzu (skip if using bottled yuzu juice). Thinly slice the peppers and set aside.
In a small bowl, add the soy sauce, lemon/yuzu juice, and olive oil. Whisk until olive oil is emulsified into the sauce.
Take the fish out of the freezer. Using your sharpest knife, carefully slice the filet against the grain into 1-2 inch long pieces.
Once sliced, arrange the hamachi in a plate or bowl however you like. I recommend a circular arrangement.
Re-whisk the dressing to ensure it is emulsified, then slowly pour into the center of the circle, so that the dressing surrounds the fish and doesn't go on top of any slices.
Gently place the jalapeño slices on all of the slices, or you can choose to place it on every other slice.
Sprinkle aleppo pepper (or red pepper flakes, or omit) over the top along with flaky sea salt and fresh cilantro leaves.
Serve chilled and enjoy!