Cook the udon noodles as the label directs. (Don't overcook or they will get mushy.) Drain, reserving about 1/3 cup of the cooking water.
Meanwhile, heat 2 tablespoons oil in a medium skillet over medium heat. Pat the tofu dry and season all over with salt and pepper. Add the tofu to the skillet and sear until golden brown, about 2 minutes per side. Set aside and keep warm.
Add 1 tablespoon oil and the greens to the skillet. Cook, tossing, until just wilted. Add the scallions, red pepper flakes, the remaining 1 tablespoon oil, the soy sauce and sugar. Add the reserved cooking water; heat to create a broth. Divide the noodles and greens among 4 bowls and top with the tofu.
Courtesy of Food Network Magazine, Photography by Antonis Achilleos