Bring a large pot of salted water to a boil for the noodles. Peel and thinly slice the onion. Trim about 1 inch off the gai lan stems and chop the remainder into bite-sized pieces. Peel and thinly slice the carrot into rounds. Shred the cucumber on the large side of a box grater. Drain the tofu and pat dry with paper towels. Cut the tofu into 1 inch cubes.
Place a large nonstick skillet over medium-high heat with 1 tbsp vegetable oil. Once the oil is hot, add the cubed tofu and a pinch of salt and pepper and cook, tossing occasionally, until browned in places, about 4 to 5 minutes. Transfer the crispy tofu to a plate.
Return the skillet to medium-high heat with 1 tsp vegetable oil. Add the sliced onion and cook, stirring occasionally, until it begins to brown in places, about 2 to 3 minutes. Add the sliced carrots and chopped gai lan and cook until the vegetables are tender, about 2 to 3 minutes.
Once the water is boiling, add the rice noodles and turn off the heat. Stir the noodles and let sit, stirring occasionally, until tender, about 8 to 10 minutes. Drain and rinse noodles under cold water to stop the cooking process.
Add the cooked rice noodles to the skillet with the vegetables, spreading them out, and turn the heat to high. Add the coriander, cumin, tamari, and as much chile garlic sauce as you’d like, and cook until the noodles are well coated and hot, about 3 minutes. Turn off the heat.
Halve the lemon and cut half into wedges. Add the juice from half the lemon to the skillet, off of the heat. Season the noodles with a pinch of salt and toss well. To serve, pile the noodles onto large plates. Top with crispy tofu, shredded cucumber, peanuts, and lemon wedges. Enjoy!