1. Cut tofu into 3/4-inch-thick slices. Place tofu slices in a single layer on several layers of paper towels; cover with additional paper towels. Let tofu stand for 30 minutes to drain, pressing down occasionally. Remove tofu from paper towels, and cut into 3/4-inch cubes.
2. Preheat oven to 350°.
3. Combine 2 tablespoons peanut oil, tamari, and 1 teaspoon Sriracha in a large bowl, stirring well with a whisk. Add tofu cubes to tamari mixture, and toss gently to coat. Let stand for 15 minutes. Remove tofu from bowl with a slotted spoon; reserve tamari mixture in bowl. Arrange tofu in a single layer on a foil-lined baking sheet coated with cooking spray, and bake tofu at 350° for 10 minutes or until lightly golden.
4. Cook udon noodles according to package directions, omitting salt and fat. Drain and rinse with cold water; drain well.
5. Combine 6 cups water and salt in a large saucepan over high heat, and bring to a boil. Add Broccolini to pan; cook for 3 minutes or until crisp-tender. Drain and plunge Broccolini into ice water; drain well. Chop Broccolini.
6. Add remaining 3 tablespoons peanut oil, remaining 1/2 teaspoon Sriracha, rice wine vinegar, ginger, and sesame oil to reserved tamari mixture in bowl; stir mixture well with a whisk. Add baked tofu, udon noodles, Broccolini, and 1/2 cup thinly sliced radishes to bowl; toss gently to coat. Sprinkle salad with cashews.