Sprinkle the tuna with the salt and dried herb mixture, place in an airtight container, and refrigerate for 30-45 minutes.
Make the leche de tigre.
Rinse the tuna and pat dry with paper towels. Angle your knife at 45 degrees and make thin 1/4″ thick cuts against the grain. Place the slices in a bowl and add the leche de tigre, turning gently to coat.
Remove the tuna from the liquid and divide among individual serving bowls. Spoon enough liquid into each bowl to just cover the bottom. Garnish with avocado, grapefruit, cucumber, radishes, and jalapeño.
Leche de Tigre
1 carrot, peeled and cut into 1″ pieces
1 cucumber, peeled and cut into 1″ pieces
1 small red beet, peeled and cut into 1″ pieces
1 small red onion, cut into 1/2″ thick slices
3 tomatoes, cut into 2″ pieces
1/4 fresh lime juice
1 cup coconut water, or more to taste
3/4 cup fresh grapefruit juice
Juice the first 6 ingredients in a juicer.
Combine the juices with the lime juice, coconut water, and grapefruit juice. Mix well and season with salt. Set aside.
If the mixture is too spicy, add more coconut water.