Microwave or steam broccoli until crisp-tender; drain.
Combine peanut butter, soy sauce, sugar, water, and lemon juice; mix well. Add scallions, garlic, ginger, and additional seasonings (hot sauce, sesame oil). The sauce will look curdled, but it will smooth out when cooked.
Boil the noodles. Meanwhile, pan-fry the tofu. Add the drained noodles and broccoli and toss to heat evenly. Add sauce and toss to combine thoroughly and heat through. (If your tofu is crumbly, as mine usually is, you can pan-fry it, take it out, and add it back just before serving.)