Press the extra firm tofu for 15 minutes to remove excess moisture, then cut into 1-inch cubes.
In a small bowl, whisk together the tamari, rice vinegar, toasted sesame oil, grated ginger, minced garlic, and red pepper flakes.
Heat the avocado oil in a large skillet or wok over medium-high heat.
Add the tofu cubes to the skillet in a single layer and sear for 8-10 minutes, turning occasionally until all sides are golden and crisp.
Toss in the broccoli florets, snap peas, and sliced red bell pepper, stir-frying for 4-5 minutes until the vegetables are tender-crisp.
Pour the prepared sauce over the tofu and vegetables, tossing constantly for 1-2 minutes until the sauce thickens and coats everything evenly.
Remove from heat and sprinkle with sesame seeds before serving.