Follow these steps carefully for the best results:

1. Press the Tofu (Essential Step!): Remove the tofu from its packaging and drain the excess water. Place the block on a plate lined with several paper towels or a clean kitchen towel. Place more towels on top and weigh it down with something heavy (a cast-iron skillet, a few cookbooks, or a tofu press). Let it press for at least 30 minutes, or ideally 1 hour (or even longer in the fridge if time permits). The longer you press, the firmer and crispier your tofu will be as more water is expelled.
2. Prepare the Tofu: Once pressed, cut the tofu block into uniform ¾-inch cubes. Place the cubes in a medium bowl. Drizzle with 1 tablespoon of soy sauce (or tamari) and gently toss to coat. Sprinkle the 2 tablespoons of cornstarch over the tofu and toss again until each piece is lightly and evenly coated. This coating is key to the crispy texture.
3. Make the Lemon Sauce: In a small bowl or measuring cup, whisk together all the sauce ingredients: ¼ cup soy sauce (or tamari), ¼ cup lemon juice, ¼ cup vegetable broth (or water), 2 tablespoons maple syrup (or agave), 1 tablespoon cornstarch, 1 tablespoon toasted sesame oil, minced ginger, minced garlic, and optional red pepper flakes. Whisk until the cornstarch is fully dissolved and the sauce is smooth. Set aside.
4. Prepare the Vegetables: Wash and chop all your chosen vegetables into bite-sized pieces. Keep them separated as they may have slightly different cooking times. Slice the scallions, keeping the white/light green parts separate from the dark green tops (the tops are often used for garnish). Having everything prepped (mise en place) makes the stir-frying process smooth and fast.
5. Cook the Tofu: Heat 2-3 tablespoons of neutral oil in a large skillet or wok over medium-high heat. The oil should be hot enough that a piece of tofu sizzles immediately when added. Carefully add the coated tofu cubes in a single layer, ensuring not to overcrowd the pan (cook in batches if necessary). Fry for 4-6 minutes per side, turning occasionally, until golden brown and crispy on most sides. Use tongs or a spatula to turn them gently. Once cooked, remove the crispy tofu from the skillet and set it aside on a plate lined with paper towels.
6. Stir-Fry the Vegetables: Add the remaining 1 tablespoon of oil to the same skillet over medium-high heat. Add the firmer vegetables first – in this case, the broccoli florets and sliced carrots. Stir-fry for 3-4 minutes, stirring frequently, until they begin to soften slightly but are still bright and crisp.
7. Add Remaining Vegetables: Add the red bell pepper pieces and the white/light green parts of the scallions to the skillet. Continue to stir-fry for another 2-3 minutes until all vegetables are tender-crisp (they should still have a slight bite). Avoid overcooking – mushy vegetables are the enemy of a good stir-fry!
8. Combine and Sauce: Give the prepared lemon sauce a quick whisk again (as the cornstarch may have settled). Pour the sauce over the vegetables in the skillet. Bring the sauce to a simmer, stirring constantly. It will thicken quite quickly, usually within 1-2 minutes.
9. Return Tofu to Skillet: Add the cooked crispy tofu back into the skillet with the vegetables and sauce. Gently toss everything together to ensure the tofu and vegetables are evenly coated with the glossy lemon sauce. Cook for just another minute, allowing the tofu to heat through.
10. Finish and Serve: Remove the skillet from the heat. Stir in most of the dark green scallion tops (reserving some for garnish, if desired). Taste and adjust seasoning if needed (more lemon juice for tartness, a tiny bit more sweetener if desired, or a pinch of salt/soy sauce for savouriness).
11. Garnish and Enjoy: Serve the Lemon Tofu Stir-Fry immediately over your choice of base (like fluffy rice or quinoa). Garnish with toasted sesame seeds, fresh cilantro or parsley, the remaining scallion greens, and extra lemon wedges on the side.