Combine all of the dressing ingredients in a bowl or a glass jar with a lid. Whisk or shake; taste for seasoning (add more salt if needed). Set aside until ready to use.
Brush both sides of each tuna steak with 1 teaspoon oil. Season them with salt and pepper. Place the sesame seeds on a large plate and gently press both sides of tuna steak in sesame seeds to coat.
Heat 1 tablespoon of oil over medium-high heat in a large non-stick pan. Add tuna steaks and cook for 1 minute- without touching them. Turn the steaks brush with 1-2 tablespoons of the dressing and cook for 1 more minute. Place the steaks on a cutting board and slice into cubes or slices.
Place baby arugula, avocado, cucumber, mango, radish, scallions, and jalapeno in a salad bowl; gently stir. Top with tuna (and all of its juices). Garnish with crispy won-ton strips.
Pour about 1½ to 2 inches of oil into a deep, heavy-bottomed pan. Heat to 360º Fahrenheit. Quick fry the strips until golden brown. Transfer to a paper towel lined plate and season with salt.