- To make cucumber broth, juice English cucumbers, sending pulp back through juicer until all juice is extracted. In a small mixing bowl, whisk together cucumber juice, simple syrup, Pernod, and fish sauce until fully incorporated. Reserve in refrigerator until ready to serve.
- Next, make the salad. Shave cucumbers and red onion using a mandoline. In a small mixing bowl, whisk together vinegar, sugar, ½ teaspoon salt, and black pepper until salt and sugar are fully dissolved. Add cucumber, red onion, and mint, and toss to combine. Refrigerate. For best results, make 2 hours in advance.
- In a small sauté pan, toast coriander and fennel on low heat until fragrant, about 3 to 5 minutes. Remove from heat and let cool. When cool, grind seeds in a coffee grinder or mortar and pestle. Rub tuna with oil, salt, and ground coriander-fennel mixture.
- Coat cast-iron skillet with enough oil to cover bottom of pan. Heat pan over medium-high heat for 3 minutes. Place tuna in heated pan and sear on all sides, 1 minute per side, or until it gets a nice sear, and is rare to medium-rare. Remove from pan, and let rest in fridge.
- To assemble, place vinegar cucumbers in bowl. Ladle broth into same bowl about ½ inch up the sides. Slice tuna into ½ inch thick slices and fan over top. Garnish with smoked almonds and scallions.