Cook soba noodles according to package directions, omitting salt and fat; add edamame for last 3 minutes. Rinse with warm water; drain well.
Combine 2 tablespoons soy sauce, lime juice, chili sauce, and sesame oil in a medium bowl. Add soba mixture and cilantro; keep warm.
Combine white and black sesame seeds in a shallow dish. Coat tuna with cooking spray, and sprinkle evenly with salt. Coat both sides of each steak with sesame seeds, pressing gently to adhere. Heat a large nonstick skillet over medium-high heat. Add oil to pan; swirl to coat. Add steaks to pan; cook for 3 minutes on each side or until desired degree of doneness. Slice tuna thinly against grain. Serve with noodles.