Preheat the oven to 450°F. Line 2 baking sheets with parchment paper.
Cut the cauliflower into small florets. In a large bowl, combine the cassava flour, water, garlic powder, sesame seeds, salt, and pepper. Whisk to combine. The resulting batter should be fluid but thick--thick enough to coat a piece of cauliflower and pool only slightly once set on the baking sheet. If the batter is too thick/pasty, add water by the tablespoon until you reach the proper consistency.
Drop the cauliflower florets into the batter and stir until all pieces are coated. Using a fork, carefully transfer battered cauliflower to the baking sheets, leaving 1 inch of space around each floret.
Bake the battered cauliflower for 20 minutes. While the cauliflower is baking, make the sauce. In a small saucepan combine the tamari, maple syrup, sesame oil, rice vinegar, tomato paste, chili paste, garlic, ginger, and sesame seeds. Bring the sauce to a boil on the stove over medium heat. Simmer for 5 minutes or until slightly reduced. Set aside.
After cauliflower has baked for 20 minutes, remove and let cool slightly. Once it's cool enough to handle, transfer the par-baked cauliflower to a large bowl. Cover the cauliflower with all but 1/4 cup of the sesame sauce. Toss to thoroughly coat the cauliflower.
Bake the cauliflower for another 15-20 minutes, or until the edges are starting to darken. Depending on positioning in the oven and just overall hotness of your oven, you may have to take them out of this second bake sooner. Just keep an eye on them! Remove the cauliflower when the sauce has “set” around the edges and all florets are a deep golden brown. Let the Cauliflower sit for a full 5 minutes before serving in lettuce wraps, on rice etc., drizzled with remaining sauce and topped with extra sesame seeds, and chopped green onions.