Cook soba noodles in a large pot of salted water until al dente, about 10 minutes. Drain, and then rinse with cold water; set aside.
Heat 1 tablespoon oil in a large nonstick skillet over medium-high heat; add tofu and season with salt. Cook, tossing occasionally, until golden, 12 to 15 minutes. Transfer to a plate; set aside.
Heat remaining tablespoon oil in same skillet over medium-high. Add bell peppers, broccoli, bok choy, garlic, and red pepper flakes; season with salt. Cover (pan will be very full) and cook, tossing occasionally until vegetables are crisp-tender, 8 to 10 minutes.
Meanwhile, make sauce: In a small bowl, whisk together almond butter and 2 tablespoons water, then whisk in vinegar and soy sauce. Add reserved noodles, tofu, and sauce to pan with vegetables. Cook, tossing until noodles are heated through, 2 to 3 minutes.